Tuesday, October 08, 2024
Initial Experiments With Tin (II) Chloride
To make a conductive spot on the glass bed I thought I might try a tin oxide layer. This is/was used in LCDs etc. to make the glass conductive. First, you need tin (II) chloride. I have tin in the form of "lead-free pewter" or I guess I could buy some lead-free solder.
I partially dissolved 8g of tin (I've left it dissolving) in 10ml of 24% w/w hydrochloric acid in a beaker. The reaction is quite slow even at 65C in my crude water bath, so you want smaller bits of tin than I used. I wore safety glasses, used ventilation, and avoided creating any Vik Chloride.
Part way through the reaction a drop was placed on a microscope slide and heated with a blowtorch until the droplet went black, then white. Predictably, the slide shattered, however the piece with the sample on remained mostly intact.
The conductivity across this ugly sample is approx 800K, and the sample is far too thick. But, tin oxide there you go.
To improve this I'll wait until the tin has dissolved as much as it will, and dilute the solution by 100x. I recall you're supposed to leave a bit of tin in there to discourage hydrolysis. Then I'll spray that onto a pre-heated slide, >800C. This time I'll use a hot firebrick to add thermal stability. Hopefully that will create a finer - prettier - layer of tin oxide and not shatter the glass. I have previously done this on borosilicate to create iridescent art, but used commercial tin chloride.
I won't cover the whole glass bed to preserve its smooth surface. I'll just have a conductive patch for zeroing the Z probe. The tin oxide may block UV, so might also serve the purpose of protecting the resin reservoir.
I go for another eye operation next week, which puts another bump in the developmental road, but after that my eyesight should be fully restored. In the meantime I can't play with fuming acids, dust etc. after the op for 10 days.
