Continued from the last two weeks, here is the final installment of The Witch Mask.


With the witch mask exterior painted and sealed, the internals were applied.  The interior was painted black with acrylic paint and sealed with Mod Podge.  I wanted to avoid using a strap around the back, as I have found that is unreliable for keeping things on without slipping.  Instead, I opted to use a hat.  Cutting the bill off of a baseball cap, the fabric was glued in place with hot glue.  Sheer black fabric was placed over the mouth and eye holes, as pictured below.  When pulled taut, this allows the wearer to see through the fabric while not allowing others to see the eyes.  The fabric was glued in place with PVA.  To keep the fabric taut, masking tape was used while the glue was drying, and it was removed upon completion.

Mask internals showing hat, blackout fabric, and paint

A hood was sewn to fit around the mask.  Made from black cotton quilting fabric, the forward opening of the hood fit directly to the mask edge.  This was secured with hot glue.  Remaining black cotton fabric was sewn into an impromptu robe.


A nest of hair was made for the witch mask.  The material I chose to use was raffia.  This fiber is produced from the frond of the raffia palm.  While you might have seen this material used in twine or hats, it is also used in traditional African tribal masks.  The raffia fibers were combed parallel to each other and folded in half.  Along the fold, a double stitched seam was sewn to hold the fibers together.  The stitch distance was short enough to penetrate most of the individual fibers so they would be retained during use.  The hairpiece was secured with staples to the paper mache portion of the mask and sewn onto the black hood with some quick stitches.

Witch mask hair made from raffia fibers

The Completed Witch Mask with Costume

Pictures of the completed mask can be seen below.  The lighting isn’t great, and the photos don’t capture dark, unnerving quality this has.  I blame my old phone for the poor picture quality.

The witch mask, completed

I wish the gloves matched the robe.

Tales of Terror

As you can tell from the previous photo, I made the mask into a complete Halloween costume.  Since I’m an adult, I naturally decided that I would wear the costume around town.  On my walk to work, I received plenty of stares.  The best part was when I took the elevator to my office.  I got on the elevator, let the doors close, and squatted in the corner near the buttons.  I did not speak.  The next few times someone would come on the elevator, I would slowly arise from my squatting position to my full standing height.  Eventually, someone went to my floor, and I got off to get some work done, but not before I scared one of my colleagues so badly, he refused to take the elevator.

On my way home from work, took the same path back.  Possibly my favorite reaction occurred when I passed by the library and two guys started shouting at me about how scary/awesome I was.  I ignored them for a beat, stopped, and turned my mask toward them while keeping my body rigid.  They screamed like little girls and ran off, the perfect reaction.

I noticed two people running towards me at one point.  One held a camera, the other a microphone.  They were interviewing people on campus for a Halloween special.  I was very excited to be interviewed.  Yet, my commitment to staying in character is very strong.  I remained silent.  All the microphone would pick up from the witch mask’d man was a deep rasping of breath.  The only motion I made to the camera was a slight tilt of my head, staring directly forward.  The interviewers loved this, but I could tell they wanted more.  After about 5 minutes of footage, I just walked away.

Since Halloween fell on a Friday that year, there were loads of parties around town.  I decided that the witch mask needed to go make some friends.  I stopped at my usual bar at one point, and I just stared at the bouncer.  Later, talking to him, I found out that this actually freaked him out pretty bad.  At the time, he remained stalwart, laughing off the fear and asking for my ID.  Since I forgot my wallet at home, I decided I didn’t need a drink that night.  No, the fear sweat would sustain me.

My last stop was a fraternity/sorority party at a house near my apartment.  I stood outside on their lawn while I could see them staring at me through the blinds.  As the watching individual turned to tell her other scantily clad friends about the creepy thing in the yard, I would dash forward and freeze, mimicking schoolyard red-light-green-light games.  Eventually, I made it up to their door, and they were truly terrified.  I stood there, and I was about to leave when some guys came out and confronted me.  One pulled my mask off, which I found rude, but I suppose I can’t complain since I was being creepy.  Leaving with a “I’ve been kicked out of better parties than this”, I decided to end my night.

To this day, the Witch Mask hangs on my wall.  A solemn visage to give visitors pause when they enter my home – a real conversation starter.


Continuing from last week’s post, here is part 2 of The Witch Mask.

Designing the Face

After several more layers of my special paper mache/plaster mix, the mask has been built up to a the final texture.  For this mask, I believe I have 5 more layers since the first two I showed last week.  The top layer is sanded slightly to remove most of the major surface defects.  I wanted to keep the surface slightly unfinished for this project, as I was hoping to evoke a sense that this witch mask was produced in a rough, imperfect manner.

The face design is similar to the inspiration.  The eyes and mouth are cut with a Dremel tool.  The cuts are very shallow on the mask.  Cutting into this material is not as simple as it seems.  Deep cuts can cause the cut wheel to snag due to the flexibility of the material.  Yet the high strength requires mechanical cutting to pierce the repeated PVA and gypsum layers.  The cuts end up turning brown due to burning from the friction.

Witch Mask, first cuts.

After using a dremel for the shallow cuts, the final cuts are made with a thin chisel.  A razor blade is used to cut out any remaining ridges inside.  Finally, the interior of the open areas are sanded down with the Dremel, giving an even texture for working.

The shallow cuts are finished with other tools


The first layer for this project was a tan acrylic paint.  Darker browns and black are used to texture the first layer of paint.  Certain areas receive more attention than others for the shadowing colors.  Contours of the mask are shaded and highlighted to give depth to the relatively round surface.  Although the witch mask is not meant to look like a real human skull would, shading is applied to certain areas such as the cheekbone.  The lips are painted red, and the teeth are white.  This was done in a sloppy manner to fit with the theme of the piece.  Edges of the eyes and mouth are painted black where the cuts took place.  I wanted the final product to be a very obvious facade.

Paint is applied.  Looks like a rough makeup day.

After the mask was painted, the paint surface was roughened with mid-grain sandpaper.  This roughening helps remove the obvious brush strokes from the mask and age it.


Additional shading was added using carbon soot.  A candle was lit, and the mask was held close above the flame.  The point was not to burn the mask, but make it look burnt.  Soot from the candle would collect on the mask when done properly.  By angling the mask over the flame, the soot collected on the surface in different sorts of strokes.  A little practice is recommended first before trying this at home so you don’t burn your artwork and so you can get a feel for how to “brush” the soot.

For this mask, I sooted the eyes near the bridge of the nose, the underside of the eyes increasing near the edge, the actual edge of the mask, under the nose, and between the teeth.  The carbon was blended in certain places with my finger.

To seal in the paint and soot, several layers of Mod Podge were applied.  Since soot may run in water based environments, I elected not to brush on the Mod Podge.  Instead, I dabbed it on for the first layer.  This produced an uneven surface at first, but this effect was minimized by adding more layers.

Soot is added for shading

To be continued…


In early 2014, I was inspired to make some mask art.  The final piece has no proper name, but I refer to it when speaking to others as “The Witch Mask”.  Work on the mask was undertaken over several months, finally completed in October 2014.  This post and the related follow up posts will detail the creation of this mask from concept to reality.

Inspiration 1 – Israeli Stone Mask

The original inspiration for the creation of the witch mask came from two sources.  First, was an article on the world’s oldest masks going on display in Jerusalem.  An article in National Geographic goes over the exhibit.  One of the masks in particular caught my eye as something creepy and unnatural.   Among the finds recovered from Nahal Hamar is this Neolithic stone mask:

Israeli Neolithic stone mask ca. 7,000 BCE

It is reported to be ~9,000 years old.

This unnamed piece was discovered in the vicinity of Horvat Duma by a farmer.  The journey from field to find is slightly unpleasant as well.  According to the story, the mask was purchased from the farmer who discovered it by Israeli general Moshe Dayan.  However, Gen. Dayan was not the nicest guy.  While he fancied himself an archaeologist, he acquired much of his collection through shady means.  An article by Raz Kletter (see § 4.3) pulls quotes from the various memoirs of Gen. Dayan relating how he did not actually purchase the mask, he just paid the driver to take him there.

The emptiness of the mask’s expression and the sordid tale to accompany it makes for some interesting inspiration.  But it took a second source to produce my idea.

Inspiration 2 – Witch

The image below is a digital painting I found while browsing around Reddit.  The work as I saw it had no source to accompany it at the time, but it struck a chord with me.  The empty expression, the facial features, and the darkness produced a connection to the Israeli mask.  Even if they weren’t related by, there was a certain kinship to them.  At that point I was inspired to create.

"Witch" by Maaria Laurinen

With post facto research, I have discovered that the illustration is entitled “Witch”, appropriately enough.  It was published to DeviantArt around 2008 or 2009 by Maaria Laurinen.  You can view more of her work here and here.

The First Layers

The witch mask was started with an oval ring cut from matboard.  The oval hole in the center had an opening with an approximate size to fit my face.  Using matboard gave me a flat surface to start building up the contour.

The face was produced in a layered process using a paper mache variant I enjoy using.  I create this using shreds of old printouts from the lab.  The first step is to grind the paper with water in a blender to produce a slurry.  Then I press out the water using cheesecloth.  The still wet paper mash is mixed with white glue (polyvinyl acetate) and plaster of paris (anhydrous calcium sulfate).  The glue gives helps bind the paper shreds together, and the plaster provides weight and strength.  The final texture of the material is like an old fashioned plaster cast.  It makes for a nice stone-like feel.

First Layers of the witch mask

A side view of the first two layers.

For the start of the witch mask, I did domed shape with a nose on the first layer.  Each layer, after drying for several days, is coated with matte surface Mod Podge or sealant to keep the things together.  In this case, drying the first layer was accelerated by placing it in an oven.  Use of the oven degrades the PVA white glue, causing the slight browning of the first layer shown above.  The matte surface is important, as it lends greater surface area for future layers or paints to bond to.  Pictures above depict the front and side view of the mask after the inital domed/nose layer, Mod Podge, and the start of the second layer.

After everything was dried and coated, I tested the fit of the mask for the first time.

A blank slate.

To be continued…

3D Printed Sheath for 8-in Chef Knife

I was recently gifted a new Shun knife without a sheath.  Obviously, I did what any normal person would do – I designed my own custom 3D printed sheath.

The perfect cover, a 3D printed sheath for my chef's knife.

The Design

The original design is based on the Shun DM0706 Classic 8-Inch Chef’s Knife. The curvature of the blade is similar between knives, and the hollow portion for the blade was given ample room to accommodate other variations. The opening of the sheath is directional, there is a simple clasping architecture to hold the sharp bits in place. For my print and my knife, this is very tight, which is what I wanted. It takes some muscle to unsheath the blade, making it a bit more child/idiot-safe.

The blade fits tight the custom opening.

An external comparison.

This wireframe image lets you see how the interior of the sheath is shaped.

The Pizzazz

I wanted to add a little something extra to the design of my 3D printed sheath, so I decided to add some lettering.  As I have more than one Shun knife with very similar handles, I added some lettering to denote that this was a 3D printed sheath for a chef’s knife.  So, I created some raised letters on the edge of the sheath which read CHEF in a narrow Impact typeface.


I’m quite happy with the design.  The curvature has a nice exotic feel to it, and the lettering adds that extra “something”.  I am very happy with how tight the fit is for the blade, as I like to feel secure that the knife won’t be slipping free any time soon.  My other Shun knife is responsible for a non-trivial flesh wound, so I am especially concerned for safety with these amazing extra-sharp kitchen razors.

The Part

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

Just want to try the parts out for yourself?  The  .stl file you will want to download is below.


DIY Bone Conduction Headphones

EDIT 07/18/17: This post has been getting a lot of hits lately. Since I don’t have comments enabled for my site, if you have questions or would like to comment on anything, please feel free to email me directly. My email can be found on my CV (I won’t post it here so the spam bots don’t eat me!)

I discovered something fascinating while browsing around the other day: headphones that transmit sound directly to your skull.  This method of sound transfer has been dubbed bone conduction.  All you do is press the little transducers up to your temple, jaw, or skull, and the vibrations in the little electrical device transfer to the waves through the solid bone medium to your inner ear.  This way you can listen to things without blocking your ears with big cans or buds.  Rather than go out and purchase one of the little premade units, I decided to make my own DIY bone conduction headphones.

I have my own issues with headphones.  I am the type who strongly prefers earbuds.  Sure, you can get better sound out of headphones, but I find that the large strap and bulky padding smashes my ears and glasses together in an uncomfortable way.  Furthermore, the shape of my skull with causes the applied pressure of the headphones to pull my glasses out of alignment.  That puts pressure on one side of my nose or the other, and it makes my vision all out of alignment.  To make things just that much worse, my very fine hair is easily molded, a quality that makes it easy to get ready in the morning but causes instant hat hair.  Headphone bands give me this weird wave in my perfect, voluminous follicle coif.  If you look at the bone conductivity headphones available on the market, they all use a strap to keep them in place like a normal pair of headphones.  With the extra pressure required to push the transducers up to my jaw, I can only imagine that they would have even more issues.

So I thought to myself: how can I make a set of DIY bone conduction headphones with properties closer to earbuds?

Answer: use the straps that you wear every day, your glasses.

The Build

For this build, I purchased equipment from Adafruit which was very similar to the stuff recommended in the Ruiz Brothers build.  I used

I followed the build similar to the Ruiz Brothers instructions linked above with substitutions made for the parts I sourced elsewhere, such as the battery pack.

I glued the completed breadboard to the battery pack and called it a success.  My first tests (using the transducers on my apartment’s door to introduce my partying neighbors to Norwegian black metal) proved the build to be a success.

For future modifications to this, I plan on soldering a jumper on the gain pins instead of using the removable jumper.  I also would wire the headphones directly to the board rather than using the European headers included with the breakout board.

The amp circuitry and transducers for the DIY bone conduction headphones.

The Buds

As you can see in the picture of the build, there are these strange brown boxes wired to the device.  These are the containers for the bone conduction transducers.  These were designed in Fusion360 to fit the transducers quite snugly.  The Adafruit page offers a technical drawing of the transducer, but I found that my units were slightly off of this specification.  I wanted the transducers to fit in the housings without much room to rattle and lose volume and quality, so I went with my measurements.

These are the housings for the bone conductor transducers.

The hooks on the end of each housing are designed to fit onto the earpieces of my glasses.  The plastic glasses I wear have a slightly tapered profile.  This means with a little push of the parts onto the earpieces, they stay in place without sliding off.  The inside of each of the hooks on the housing are slanted, e.g. one end is more open than the other.  This means that the housings are not interchangeable, and fit on either the left or the right side of the glasses.  The cover of the housing fits into the remaining room around the transducer and these can be glued into place.  The slit at the bottom provides enough room for my cheap wires to go through or a bit bigger gauge if you are concerned about sound quality.

The parts fit onto the earpieces of my glasses.

The housings were printed on a Makerbot 5th Gen in dark brown PLA filament.  The print was scaled at 102.4% from the actual design size.  This scaling was based on a previous calibration curve of the printer PLA shrinkage and print accuracy.  Like I said, I wanted the tightest tolerance the little 3D printed parts could manage.

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

This is the “left” container.

This is the cover which fits over both the “left” and “right” versions of the above model.

Just want to try the parts out for yourself?  The three .stl files you will want to download are below.






The Fit

With my little DIY bone conduction headphones complete, it is time to try them out.



A handsome man with his DIY bone conduction headphones

Look at that handsome fellow in the picture.  The transducer housings fit as expected on my glasses.  The sound transferred well to my skull.  If you have ever used bone conducting transducers before, think of it like a medium press sound transfer rather than a super hard press.  The brown color is still stands out a bit from the color of my glasses and my hair.  Finishing paint would be necessary to make it look nicer.

The sound quality was pretty good as far as these little transducers can go.  They won’t be replacing my in-ear monitors any time soon, but they are sufficient to listen to spoken word audio.

Bonus trial: my mother is partially deaf due to Meniere’s disease.  She tried my DIY bone conduction headphones and was able to hear things on better on her deaf side.  Further development of this technology may prove to be useful for sufferers of mild hearing loss who do not desire the full hearing aid.

The Purchase and Return of a Makerbot Replicator+

Minor note: I got my PhD the other day.  No big deal.  The important part of the story is that I got a sweet graduation present from my mom.  She bought me the 3D printer of my choice.  Talk about awesome!  I decided to go with a machine I have had some experience working on/with in the past, a Makerbot.  There were a lot of options out there, and some of those alternatives had pretty great reviews.  I decided to go with the latest Makerbot model.  It wasn’t until I had gotten up and running that I became aware of some of the major Makerbot Replicator+ issues.

The Good

Before I really hand a chance to grasp the Makerbot Replicator+ issues, I had a lot of fun with the unit.  The setup was a breeze and I was printing as soon as the extruder warmed up.  In addition to some of my own designs, which I will give individual attention later, I printed off designs that are easy to find on the Thingiverse site.  My favorite print was a fully articulated pangolin.
Save the Pangolins
Save the Pangolins from the side

This cuddly little creature was produced as part of a project to raise awareness about pangolin exploitation, the most trafficked animal in the world.  There are some poorly educated people out there that believe that the pangolin scales have magical healing powers.  Additionally, they are a very popular bush meat item.  Despite being illegal to buy and sell in many parts of the world, the ever wonderful homo sapiens manages to make a buck from these little mammals.  The Save Pangolins campaign aims to eliminate this illegal trade.

The print itself turned out quite well.  This was the first big print on the Replicator+.  The details came out fine and it feels quite nice.  I did have some issues getting everything perfect.  The final tail joint and the forelegs did not articulate.  This print was made before I had started fine tuning settings like extruder pull, so some stringing between these tight joints may be the cause.

The Bad

I discovered that when printing flat surfaces, I would see some bizarre defects.  The layer deposited on the surface would form melted waves.
Waves from the side

I printed off some test swatches and observed them.  The extruder head was dragging along the edge of the recently printed strand of the current layer.  This was causing the last few printed lines to begin to curl with the direct heat transfer from the extruder.  The weirdest part was that it only happened in one direction.  As layers were stacked, the Makerbot Replicator+ issue would only propagate along the X coordinate.  If a layer was printed in another direction, no issues:
A flat surface

Here is a side by side comparison of what the issue was:
Side by side

Something was clearly not right with the setup of the printer.  In the true spirit of Maker culture, I decided to find a solution to the problem.  I told the printer to recalibrate the z axis.  If the printer head was dragging along the side of a print, it would make sense that the printer bed height or z axis motion was out of whack, right?  That is when the real problems started.

The Ugly

On the first print after issuing the factory supplied z axis calibration command, all hell broke loose.  During the setup for the print, the extruder dragged along the edge of the print surface.  I rushed downstairs to stop it as soon as it had started.  The scraping made some gruesome noise.  Meanwhile, the extruder continued gouging into the print bed.  The hot extruder nozzle actually melted the plastic as it scraped itself across the surface.  I did not make it downstairs in time though.  When I got downstairs, the printer had ripped the extruder out of its mount and began making panic noises.  The scene wasn’t pretty.

These are the real Makerbot Replicator+ issues, self mutilation

I sent a complaint to the manufacturer about my Makerbot Replicator+ issues.  One of my favorite snippets from that little conversation was that the end users are not supposed to level the build plate despite the fact that the option was included in the software.  The factory levels those “with lasers”.  To their credit, the customer service rep did offer to replace the unit.  This was not enough for me.  I was already soured on the unit when I couldn’t get it to interface with any of my computers, since they apparently dropped Linux support.

Now I’m awaiting the RMA results.  Besides wasting my time and getting screwed out of 10% of the unit cost for a restocking fee, I’m just plain disappointed in how far the genericized flagship of 3D printing has fallen.  I can only hope that I’ll be happier with the Ultimaker I buy when the refund goes through.


Acetone Melted Goggles

I remember back in undergrad when I had a small safety incident in one of my labs.  We were doing an extraction of . . . something or other.  Part of the experiment involved an extraction using a cooled Rotovap extraction.  This particular extraction needed a very cold trap.  We were using dry ice in an acetone bath (-78℃/-108℉).  As I was putting in a block of dry ice into the acetone, the warm (relatively speak) acetone flash sublimated the dry ice.  This  sudden expulsion of nitrogen gas splashed the acetone out of the container and all over me.  Thankfully, I was wearing my safety goggles.  The acetone splash dissolved the plastic of the clear shield on the goggles and permanently ruined it.  Thus, I now have a set of acetone melted goggles.

Acetone melted goggles
I guess they aren’t technically “melted” just a little dissolved.

My acetone melted goggles are actually a handy little accessory to have on hand.  I always take it to the first day of any lab section I teach.  When I give the requisite lecture about appropriate lab behavior, I like to pass these around.  Even if the students are fresh and don’t know about acetone on plastic or sublimation, they will recognize that goggles saved my eyes.  Hopefully the point sticks a bit better with them, and they understand the importance of safety in the chemistry lab.

Blue Canola Oil or Dye Another Day

Did you know that if things go just wrong enough, you can create blue canola oil?  I didn’t either until the other day when I decided to make some fries to go with some burgers I made.

Hungry Yet?

It was going to be a delicious meal.  Some big Idaho potatoes were into thick fries (the best kind when you make them at home).  I was making sliders with ground beef and just a little bit of sausage.  I had fresh buns, salad greens, Vidalia onions, and spicy mustard all ready to go.  The fries were timed just right with the patties so that everything would be ready to go at the exact same time.  It was going to be perfect.  I grabbed a metal colander to scoop out the fries (I couldn’t find a slotted spatula), dipped it in to grab my deep fried potato prize, but suddenly my cooking oil turned a bright turquoise.

I scooped out the fries and laid them to cool on a paper plate.  The color change had gotten to the fries.  They were contaminated.  I wasn’t sure what caused this horrific turn of events, but something told me that these were inedible.

Blue French Fries

Unless it comes with the suffix -berry, I’m hesitant to trust blue food.

I was stymied.  What could create blue canola oil?  I knew it had to be linked to the metal strainer, but how?  I always thought the strainer was steel, had it magically turned into copper?  Even if it did have copper in it, how did that suddenly dissolve into canola oil?

And then the solution hit me:


Remember a few posts ago when I was going over my Model M mods?  You know, this one.  Remember how I dyed my keycaps blue?  Yeah…. about that…

It seems that I somehow mixed in my crafting colander with my food-safe cookware.  The iDye Poly I used for that project was formulated to dye polymers.  Most polymers a craft oriented person would want to color are hydrophobic in nature.  It follows that a very hydrophobic liquid (canola oil) would dissolve the dye quite readily.

Since this little event, I have separated my metal strainers in a more obvious manner.  Accidentally using lab ware for human consumption is no joke.  Now the real question: what do I do with all this blue canola oil?


Blue Canola Oil

Fountain Pen Ink pH – A Comparison of Five Commercial Inks

A while back, there was some discussion about fountain pen ink pH.  During that discussion, I offered to test inks and my friend from the Geekhack forum, CPTBadass, offered to donate some samples for my tests.  I received samples from my good CPT in the mail, and I went about running tests.  This post is the outcome of that work.

The Samples

Four samples were procured from CPTBadass and one was supplied by the author.

Noodler’s Baystate Blue – a vibrant royal blue ink
Rohrer & Klingner Scabiosa – an iron gall ink
Noodler’s North African Violet – an intense violet ink
Diamine Soft Mint – an ink that appeared turquoise or aqua in the bulk solution
Noodler’s Polar Brown – a somewhat rust tinged brown ink

Upon receipt, the samples were transferred to 20mL plastic scintillation vials.  The original containers’ opening was too small to accomodate the probe used in the pH experiments.

1. Shake Tests


Samples in scintillation vials were given a quick shake and observed for fluid and surface characteristics.


Ink Observations
Noodler’s Baystate Blue Ink left a thin layer coating the wall that persisted for a long time.  This thin layer did not show any detail of the plastic surface.  It produced bubbles,
Rohrer & Klingner Scabiosa Ink left a very thin layer coating the wall that persisted for some time.  The layer highlighted plastic imperfections of the bottle by contrast.  It produced bubbles.
Noodler’s North African Violet Ink left a very thin layer coating the wall that persisted for some time.  The layer highlighted some plastic imperfections of the bottle by contrast.  It produced bubbles.
Diamine Soft Mint Ink did not coat walls.  Preferred cohesion and formed small islands of liquid on the plastic surface.  It produced NO bubbles.
Noodler’s Polar Brown Ink left a very thin layer coating the wall that persisted for a long time.  The layer highlighted plastic imperfections of the bottle by contrast.  It produced many/large bubbles.  Bubbles appeared to grow over time.


The surface coating indicates that there was interaction with the walls of the container.  Since the plastic was either polyethylene or polypropylene, we expect the walls to be hydrophobic.  The inks which wetted the surface well interacted with the plastic surface.  Since bubbles were formed, we can assume that the interaction with the wall was due to surfactant in the ink reducing the surface energy allowing this prolonged contact.  The lack of coating in the Diamine sample suggests that it is highly hydrophilic.  The lack of bubbles suggests that no surfactant was added to the ink during manufacturing.

2. pH Test


Samples were tested for hydrogen ion concentration using a Vernier pH probe connected to a computer running the logging software.  The probe was calibrated immediately before the experiment with a pH 4.00 buffer standard (Fisher – methyl alcohol, formaldehyde, and potassium hydrogen phthalate) and a pH 10.00 buffer standard (Fisher – disodium EDTA dihydrate, potassium carbonate, potassium borate, potassium hydroxide).  The lab temperature was 25C, and the standard pH did not need adjusted from the label value based on this temperature.


Ink pH
Noodler’s Baystate Blue 3.97
Rohrer & Klingner Scabiosa 2.33*
Noodler’s North African Violet 4.60
Diamine Soft Mint 4.00
Noodler’s Polar Brown 8.78


The majority of the inks were slightly acidic in nature, and the Polar Brown ink was slightly basic.  The iron gall based ink was quite acidic.  This ink pH is marked with an asterisk(*) since the pH was not stable.  The value continually drifted downward, trending toward acidity.  The value used here was the observed pH value after 15 minutes of attempted stabilization.  After the experiments were complete, the pH probe was observed to be slightly discolored.  To determine how this effected the results, the standards were measured with the discolored probe.  The 4.00 buffer measured 3.74, and the 10.00 buffer measured 9.88.  This indicates that the results are probably skewed downward by ~0.25 pH units.  The results were not corrected for this error, since it would be difficult to quantify the error without much experimentation.  The probe was cleaned by soaking in 2% nitric acid for 30 minutes.  After this time, the probe was deemed ‘clean’ and returned to storage.

The results of this experiment should clear up a few misconceptions.  Notably, none of the inks in this less than comprehensive test were pH neutral.  Some sources discussed previously make claims based on the acid or base nature of inks based on brand.  Clearly, this is not a wise assessment.  The brand with three different inks in the test (Noodler’s) showed a wide range of pH values.  Some outside sources suggest that acidic inks may damage pens.  Most of the inks tested were acidic.  No metal based tests were performed in this experiment, but this author believes that the correlation between metal pitting and acid content of an ink may be spurious.

3. Solvent Tests


In this test, a small quantity of ink was deposited onto a strip of printer paper (Staples Brand) and partially submerged in solvent.  The ink was applied to the paper by smearing one or two drops from a disposable plastic pipette on the paper.  All labels on the samples were written in pencil.  The ink was allowed to dry then tested.  Most strips were folded so they would stand and set in a petri dish with the testing solution for five minutes. These tests were broken up into aqueous, organic, and chlorinated solvent groups to prevent unwanted reactions.

The wet papers were then taped to a rail in the hood to dry.

One strip was tested under a 18.4 W long wave UV lamp for one hour.  One strip was left as a control.



The numbers represent the inks Noodler’s Baystate Blue, Rohrer & Klingner Scabiosa, Noodler’s North African Violet, Diamine Soft Mint, and Noodler’s Polar Brown respectively.  The inks were not applied evenly, and some spreading, especially in samples 3-5 was due to large drops.  The Polar Brown ink naturally feathers a great deal on this paper, and the Scabiosa and North African Violet inks showed some feathering.  The Soft Mint ink naturally spread, but did not show feathering.


1 2 3 4 5
minimal feathering feathering feathering spread and loss No Change (NC)


1 2 3 4 5
upward drift some upward spread upward drift upward drift edge reddening


1 2 3 4 5
some spread NC feathering upward drift NC


1 2 3 4 5
upward drift some feathering some feathering/drift some drift NC


1 2 3 4 5
upward drift NC minor drift NC edge reddening

Nitric Acid (~4%)

1 2 3 4 5
gone, yellow edge almost gone, blue edge almost gone, green edge gone NC

Hydrochloric Acid (~4%)

1 2 3 4 5
gone, yellow edge almost gone, blue edge almost gone, green edge gone/upward drift edge reddening


1 2 3 4 5
upward drift feathering upward drift/feathering minor upward drift yellow color separation

UV Exposure

1 2 3 4 5


There is a great deal of information to be learned from these tests.  What we are looking at is actually a very rudimentary form of thin layer chromotography.  The paper acts as a stationary phase and the solvent as a mobile phase.  The mobile phase moves our eluent along the capillaries within the paper fiber matrix.  If we let this go for a long time, we would see the individual components separate from each other.  There are better methods to perform that experiment though, and it was not in the scope of this one.  The goal of the test was to determine the stability of the ink when in contact with the solvents.  In doing this, we can learn something about the character of the ink.

Different solvents have different polarities.  The polarity of a molecule being the concentration of electrons on one side of an atom and exposed protons on the other side.  We can relate these by a polarity index.  Since “like dissolves like” if something is moved or dissolved by more polar solvents, then the material must be polar.  So we can see that the Diamine ink is more polar than the quite nonpolar Baystate Blue based on what different solvents do to it.

The Polar Brown ink interestingly slightly drifts in both polar and nonpolar solvents.  If you look closely (probably not visible in pictures), you can see a yellow component separate out in nonpolar solvents and a red component separate out in polar solvents.  These colors moving out of the bulk drop only slightly affect a color change in the brown.

I chose the two acids to test here on purpose.  We would expect the HCl to react mostly as an acid, whereas the HNO3 would react as both an acid and a strong oxidizer.  Since both of the acids had similar effects on the inks, we can see that none of the inks oxidize easily – which speaks well for the permanence of these inks.

Future tests would include solvents with polarity index of 0.

The lack of change due to UV light is good, though this author would like to point out that this was not a very strong source.  Future tests should attempt to use more powerful sources such as a laser.

A. Errata

All solvents were obtained from Pharmaco Aaper with purity >99.5% except the nitric acid, which was obtained from Fisher.

All water used in the experiments was reagent grade, purified by reverse osmosis to resistance of >18Mohms.

I would like to thank CPTBadass again for his donations and my advisor for being out of town this week so I could do silly experiments like this without getting yelled at.

Thank you for reading, I would be happy to address any questions or comments you may have about this work.

A 3D Modeled Keyboard Cap

After I got hooked by the allure of 3D CAD, I decided to practice my skills by making a 3D modeled keyboard cap.  I started working on something using OpenSCAD, but it proved difficult to get the sort of organic curves I wanted.  I wanted to get some experience using a GUI based-program, rather than just scripting.  Instead, I decided to try a program called Fusion360.  This program is a free variant of Autodesk for personal and low-impact use.  It sadly does not have a Linux build, but I have had luck with it on my Windows box (it has the more powerful gaming GPU’s on it anyway).

The Design

I based my design on the classic caps you would get on retro units, like the Commodore.  A modern variant is available from Signature Plastics (PMK) known as the SA profile.  At the time I originally made this model (April 2015), there weren’t any of these models freely available.  This should be similar to the SA keycap dimensions but not quite the same.

The 3D modeled keyboard cap from the side.

The 3D modeled keyboard cap from the bottom.

The Real World Versions of my 3D Modeled Keyboard Cap

I decided to have these 3D printed from a commercial vendor, rather than trying to print it on a home printer.  I wanted to get some better detail.

The first print.

The height is somewhere between Signature Plastic’s DSA and SA row 3 profiles.  You can compare the shape and size in the picture below of my 3D modeled keyboard cap  to a DSA (left, in black) and an SA (right, red) profile cap:

A comparison of the print to commercial versions.

I’m glad I did this test run.  The stem shrank in a way I didn’t expect, and the cruciform is a bit too big.  It slips on and off the stems too easily.  This is an easily fixable problem.

The bottom side.


I made a new version with a tighter cruciform.  I added some text on this one.  Nothing like a little American Psycho quote to brighten up a keyboard.  I ended up giving this to a colleague as a gift.

Feed me a stray cat.


If you would like to use this file, feel free to do so.  Check it out:

This is a 3D render, play around with it!

And here is a download link.