PeterH

a sprig mould?

Which reminded me of an early paper on local reduction. One of the most interesting ideas was the use of a SiC containing engobe/slip which then influenced the colour of a SiC-free glaze applied over the bisqued piece. - They give combinations for copper reds at cones 012 and cone 9. - They suggested that silicon carbide achieves reduction effects over this remarkably wide range by only reacting when in contacted with liquid glaze. I haven't seen this idea mentioned elsewhere (and would be very interested in pointers). More detailed summary of the 1932 paper in an earlier post PS If the slip idea does work I wonder if an SiC/CMC "underglaze" would also work. PPS A full copy of the paper is now online via https://ur.booksc.eu/book/9078584/3dc696 PPPS I get the english version of this paper using this button ... your mileage may vary. If so see the later posts from those who had difficulties..

I think the wash-out isn't complete enough, and the remaining cyanotype continues to develop colour. Presumably a porous bisque surface presents greater wash-out problems than, say, paper. Especially if the cyanotype solution soaks in deeply. Some ideas in Tips for cyanotype printing on to ceramics https://maverickbeyond.com/2020/09/06/tips-for-cyanotype-printing-on-to-ceramics/ @blackthornAny input?

Might be worth glancing at DIY To the Rescue: How to Make a Frit Piston https://www.delphiglass.com/blog/how-to/diy-to-the-rescue-how-to-make-a-frit-piston Scaling it to a suitable size

Glad somebody is keeping their eye on the ball, I was getting fixated with the "on-glaze" problem. --------- Do you have any idea if their are any constraints on the thermal treatment of the photochromic ruby glass prior to exposure to UV? PS Skimming Weyl's "Coloured Glasses" suggests that: - Pre-exposure the glass is rich in both Cu⁺ and Ce³⁺. - On exposure the concentrations of Cu⁰ and Ce⁴⁺ increase. - During the strike firing the Cu⁰ atoms congregate into copper nanoparticles.

The idea of "off-label" use of ground photochromic glass-blowers glass is a bold one, but has lots of potential pitfalls. The outstanding one was mentioned early on by @Callie Beller Diesel, The differences the COE (coefficient of expansion) between this glass and your likely substrates. A problem potters have a lot of familiarity with (matching body and glass to avoid crazing or shivering). While exploring the availability of this expensive photochromic glass (and ways to reduce it to a frit of the right grain size) I suggest you make the first steps in testing if such a frit could be "fused on" in a satisfactory fashion -- where the finished article is capable of passing "stress tests". https://digitalfire.com/glossary/thermal+shock At the moment I've only got one potentially useful idea, and a wild "Hail Mary" suggestion. The good idea is to find a supplier of a coloured non-photochromic glass frit of similar COE and melting characteristics as your target photochromic glass. Fuse-on using a photochromic-glass "striking" schedule. Experimenting will be a lot easier (it's already ground) and cheaper. If you cannot get this to work , it's not worth going any further. If it does work you're good to go on your next tile: switch to photochromic frit, glue, expose, fire. My "It's a one in a million chance, but it might just work" idea it to try a sodium silicate glue to fix the frit to the glass/glaze. While details are hard to find sodium silicate has found applications in highish temperature applications (eg auto repairs: leaking cooling systems, fixing damaged exhausts). Not 100% sure of how waterproof the final product would be (clean-up of silicate glues is with hot water), but if it fixes car cooling systems? IMHO It's worth a few test-tiles. I doubt if it would solve the COE mismatch though. PS Note that sodium silicate is a generic name https://en.wikipedia.org/wiki/Sodium_silicate ... In early tests I would guard against spitting. PS 1st fact sheet I could find https://tinyurl.com/4p8k6yv3

@Callie Beller Diesel gave an excellent choice for a "pigment" way back. A coloured frit, presumably with the same coefficient of expansion as the glaze/glass and with a softening temperature chosen to facilitate fusion.

"What pigments that survive the heat" is an easy one: use ones in regular use in pottery. Such as "oxide-washes" and "ceramic stains". @blackthorn mentioned some in one of his earlier posts. Often a little frit or Gertsey borate (or it's modern substitutes) is added to aid the fusion. Temperatures depend strongly on the glaze (or glass) you're fusing onto. Glaze choice constrained by the clay body of your "pot" (must match thermal expansions). I've no idea if anybody has tried #5. You'll probably need to suck it and see ... or get lucky with literature-search/google. On the other hand if it doesn't work pretty much all avenues to fuse an "alternate photographic techniques" image to glaze/glass are probably doomed. Parting thoughts As stated pretty everywhere in these threads: test, test, test. Either it's a thought-experiment or you need to start making & firing at least some test-pieces. Perhaps join a local studio and get a little hands-on experience, and contact with potters at work. You also will only succeed if you can get all the stages (including exposing the 3d object) working right. A chain is as strong as its weakest link, and all that. Obviously you need to safely manage any fumes arising during firing. ... and I should have said that mixed-media is a legitimate choice if it satisfies your objectives. So covering an image on a porous pot with some sort of sealer might meet your needs (varnish, brick sealer, clear paint, ...) and would save a lot of hands-on learning pottery 101+. Or act as a stepping stone to greater things.

There seems to be a degree of mutual confusion. I'll explain my thoughts. Decomposition temperatures 1) If you use a method like pigment-loaded gum-dichromate (or gum-DAS) after exposure and development you finish up with an image consisting of varying thickness of pigment-loaded "gum". 2) Essentially you have created a "transfer" in-situ. Either sitting on top of a glass/glaze or within the top layers of a porous ceramic. 3) At this point the dichromate/DAS has served its purpose, and can be burned-out with the gum during the firing. 4) Hopefully the pigment will stay in sufficiently close proximity to the surface to be fused/incorporated into it during the firing. There is absolutely no need to look for light-sensitive materials with a high decomposition temperature for this process. Cyanotype You state that cyanotype "can be fired to ceramic but not to glass", a reference for this would aid the discussion. But here we go: 1) The cyanotype process precipitates out a strongly coloured iron compound, which forms a strong image. If fired this will decompose to a paler iron oxide. Here are some pix of the unfired image. I've yet to see any pix of fired image. https://tinyurl.com/8ubba93x 2) Legalistic quibble. The initial cyanotype process was a liquid process and relied on the backing material (paper,cloth, etc) to hold the precipitated compound in place. This carries over naturally to porous ceramic but not to water-proof glass/glaze. 3) A long-standing solution to this problem is the precipitate the iron compound into a layer of gelatin or similar. https://tinyurl.com/ynhzneer 4) If you want a fired-on image from such cyanotype I would just try firing them. The situation is not that different from transfers or gum-DAS images so the chances of it working are promising. 5) Do we know anybody who has tried this? How successful was the attempt? Finally photo-sensitive glass This presents a completely different and formidable set of challenges. Which I'll comment on in a separate posting.

As you are aware your link gives an article about using this product and a picture of it. On the picture you can see that it's CAS number is 2718-90-3. Aside: A CAS Registry Number, also referred to as CAS RN or informally CAS Number, is a unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature. There is an MSDS for 2718-90-3 (4,4'-Diazido-2,2'-Stilbenedisulfonic Acid, Disodium Salt) at https://fscimage.fishersci.com/msds/67032.htm There is an MSDS for 7778-50-9 (Potassium bichromate) at https://www.fishersci.com/msds?productName=AC197760050 ---------------- PS Anybody know a way of finding MSDSs in a uniform format, the disparate styles don't help comparison. PPS Google translates the warning you mention in the French-language MSDS as: Risk of explosion in case of fire. Fight fire remotely due to the risk of explosion. Be careful as it can decompose on combustion or at high temperatures and generate toxic vapors. My personal suspicion is that this is intended as guidance to fire brigades attending factory fires where there might be drums of the stuff lying about. If this is the case the warning may have little relevance to the owner of a 25/50g bottle. Although I definitely wouldn't throw it on the fire, and take due care disposing of it.

I'm old enough to have made potassium dichromate based indoor fireworks, but that was another time. Maybe @blackthorn can suggest safer/greener sensitisers/processes. These are just a couple of google hits. Gum Diazo Printing v1.4 https://www.alternativephotography.com/gum-diazo-printing-v1-4/ The present paper aims to be a reference guide to anyone in the EU willing to go on printing with pigmented gum while being fully compliant with the actual safety regulations regarding chemical substances (i.e. avoid the use of dichromate, illegal as of September 2017 in the EU). Although many people may have some leftovers of the sensitizing agent still in their cabinets, it’s hard to imagine that anyone would go on using illegal substances even in small quantities, also because health concerns have more than solid background and vast scientific literature is available documenting how hazardous the hexavalent chromium compounds can be. Also A non-toxic alternative to gum dichromate https://www.jstage.jst.go.jp/article/photogrst1964/70/Suppliment/70_Suppliment_74/_pdf/-char/en

I cannot think of any reason why iron oxide cannot be used as the "pigment" in gum-dichromatic style processes. Or any other photographic process with a wash-away binder carrying a pigment. Wouldn't keep banging on about it otherwise. [Or ceramic stains with or without a binder; eg frit or "Gerstley borate"]. PS Just trying to make the point that if you are using a photographic process involving a pigment and wash-away binder you can to some extent decouple your experiments on pigment-selection and photographic delivery. ... of course if your pigment need to be fired it's an open question how well any pigment will adhere to a 3D shape during the firing process. (I doubt that you will find a heat-tolerant adhesive.)

This suggests a variety of ways iron-oxide can be applied to a ceramic glaze. Presumably the same methods would also work on glass. DIY Ceramic Decals From Your Laser Printer (Update: and Magnetic Tape) https://www.instructables.com/DIY-Ceramic-Decals-From-Your-Laser-Printer/ ... including To get the printed image to the ceramic glaze, you can simply glue the paper on the ceramic piece ... This might enable you to test the result for its archival qualities. Before investigating alternative photographic processes to apply the iron-oxide.

I've no idea if hardened (cross-linked?) gelatin melts. If it does it might be worth trying the gum arabic form the gum-dichromate process instead. PS AFAIK the admittedly small quantities of gum arabic historically used as a glaze additive burnt-out cleanly. Use of gum arabic has largely been replaced by the use of CMC (carboxy-methyl cellulose), but I've no idea if this can be used in the gum-dichromate process.

oops, finger trouble

I'm being very careful to say as little as possible, in order not to mislead you. I'm just indicating further research might be worthwhile. If the transfer paper was much cheaper, I'd suggest doing a trial transfer with it to see how "archival" the the fused image is. [But I believe that not all toners contain iron.] If it turned out well it's likely a proof-of-concept that a refractory powder can be fused onto glass, with the burn-out of a carrier (plastic in the case of toner?).

Can I point you to this advert https://tinyurl.com/t53rvyfn Not because I think you will be directly interested in the product, but because it implies that you can [to some extent] fuse iron-oxide to [flat] glass at ~680-800°. And then slump the glass or make multi-layer sandwiches if you wish. @Callie Beller Diesel Does that sound plausible? If it works as advertised it might try fusing with a gum bichromate image rather than printed decals, and perhaps Mason stains rather than iron oxide (esp. those with spinel structure?).

I just tried and the manual is at the link @JohnnyKprovided, suggest you try again with https://community.ceramicartsdaily.org/applications/core/interface/file/attachment.php?id=14499

Look like it's Malatchi CTS Slider Pot 10k Ohm on https://www.surplussales.com//Potentiometers/Slider/Slider-1.html

Is this of any help? http://aakilns.com.au/pdf/novaman1.pdf 1st page is