Adventures in DIY spin coating (UPDATED 2/2)

I am currently working on a project that needs its glass display to look like a round green phosphor oscilloscope screen. I wanted to try and use a transparent enamel paint but guess what? No one sales hobby spray paints I need anymore and people seem to be price gouging all the leftovers!

Airbrushing is an option. ~~I have been looking into getting an airbrush to boost my skillset. So I’ve put it on the list of things to learn in the coming year.~~ I have since picked up a fantastic New Years on a Paasche Talon TG Airbrush. But at the time the only alternative I could think of would be spin coating.

I made my spin coater out of a high speed DC motor that I salvaged from some old 80s lab equipment and a cheap off the shelf DC speed controller. The watch glass is attached to a hub I made with this tacky slick surface friction disk. I don’t know how to explain it other than it’s like what you would use to prevent a cellphone from sliding off a car dash? It works amazingly well on the slick glass surface and as long as it remains clean, you can reposition the glass to get it balanced as best as you can. I have found a little wobble does not seem to cause an issue.

But what to spin? During my exhaustive search on alternatives to rattle cans, I came across this glass medium by Liquitex. I was really interested in its properties like adhering to glass, heat curability and the fact that you can tint it with transparent acrylic inks. I used a Phthalocyanine Green Yellow (Shade) to get the color I wanted.

While it took me a few tries, I eventually got the mixture of ink/medium dialed in. I wasted a little bit in the learning process as I found out that you only get one chance to spin a coat on. It does not do multiple layers . Plus I had some trouble with air bubbles getting trapped while hand stirring. I ended up using a laboratory vortex mixer to try and keep the air bubbles as small as possible. It worked very well for that I think.

I also tried using a flame to pop the bubbles like I do when resin casting but this failed and end up quickly scorching the medium. In the future, I plan on investing in a vacuum pot setup and I am guess that I could get a truly bubble free mix this way. I am waiting on an email back from the manufacture to see what they say about the De-gas method. In an email with the manufacture they say that vacuum de-gassing would be a bad Idea. It seems like this could speed up the evaporative process of the emulsion possibly damaging the medium.

Far as baking goes this glass medium must be absolutely 100% dry before oven curing to prevent what the manufacture calls boils in the emulsion coating. I used a hairdryer on low to speed up that process.

Speaking of ovens, I recently gutted the thermostat on a lightly used toaster oven and adding a cheap thermocouple based PID controller/solid state relay. I have not tried to tune the PID controller but out of the box it stayed well within the 300F for most of the 30min bake time.

After the cure time was up the best thing I found to do is to just turn off the heat and leave it alone. Don’t open the door. Let it cool slowly down as not to crack or heat stress the glass. To my amazement the heat seemed to pop some bubbles on the surface and I think it might have caused some of the others to shrink. In the end, you can not see the leftover tiny bubble blemishes in the emulsion layer from the uncoated front side of the glass. It looks like perfect.

Warning: Never use a food making oven for your projects!!! Again please do not try and bake this stuff inside your home oven. The emulsion is very fume heavy so you need some sort of active ventilation in the space you are curing this in.

In the end I could not be happier with the results! Check it out!