PeterH

As an example here is the entry on cracks http://ceramicsfieldguide.org/pdf/materials-handouts/ClayCracks.pdf

Historical aside Code stone. Sold as an artificial stone, it was really a ceramic with a very narrow firing range. Coade stone https://en.wikipedia.org/wiki/Coade_stone The Secret of Coade Stone https://tinyurl.com/y2ckdhyy What is Coade stone? https://tinyurl.com/2s3b5j76

Naming an issue, see https://en.wikipedia.org/wiki/Calcium_phosphate Tricalcium phosphate (tribasic calcium phosphate or tricalcic phosphate, sometimes referred to as calcium phosphate or calcium orthophosphate, whitlockite), E341(iii) (CAS#7758-87-4): Ca3(PO4)2 https://tinyurl.com/bdds5ssf

Scarva offer it at a higher price, but lower postage. No claim this is best UKish price available. https://tinyurl.com/2t33eypa Partially completed order for 1kg

My understanding was that everything for sale is probably mined as hydroxyapatite, but sold as either triphosphate or synthetic bone ash. Two recipes:

I think the recipe is essentially the same, substituting calcium triphosphate for bone ash. Bone china https://digitalfire.com/glossary/bone+china True bone china is a special type of translucent porcelain. Instead of feldspar as a flux, bone ash is used (today available in synthetic form tri-calcium phosphate). ... my note tricalcium phosphate is Ca3(PO4)2 Unfortunately the terminological plot thickens: Phosphate Triphosphate https://en.wikipedia.org/wiki/Tricalcium_phosphate Most commercial samples of "tricalcium phosphate" are in fact hydroxyapatite Bone Ash https://digitalfire.com/material/123 Bone ash is TriCalcium Phosphate in the form of Hydroxyapatite Ca5(OH)(PO4)3. This reacts when making bone china to give Anorthite (CaAl2Si2O8) and Ca3(PO4)2. 2*Ca5(OH)(PO4)3 --> 3*Ca3(PO4)2 + Ca(OH)2 So I've no idea if you you substitute 1:1 hydroxyapatite (sold as calcium triphosphate, or maybe synthetic bone ash) for "real bone ash". But it probably isn't far off.

I can think of two possible reasons 1) Historically that's the way bone china was [always?] produced commercially. 2) You may only get marginal transparency gains from using bone china unless you make thin and fire close to warping. When you do - you need setters and hence a high bisque. If you don't - porcelain and white-stoneware are easier to use.

... while waiting for the experts to arrive. Sasha Wardell is an artist who works in bone china, her site is at https://sashawardell.com/ Her 1st book Slipcasting contains some bone china specific information. I haven't seen her 2nd book Porcelain and Bone China but I expect it's well worth reading. She gives an overview of porcelain vs bone china in Tempting Transparency https://tinyurl.com/mryx92z7 You need to high fire first because bone china has a short firing range and tends to warp. It's usual to use setters the support the work during this firing. Obviously you cannot glaze the parts the setter touches, so glaze fire afterwards. Glazing the vitrified body is difficult. Heating the pots helps, as does spraying. Tempting Transparency https://tinyurl.com/mryx92z7 Bone china has a low-glaze cycle following low-fire clay temperature ranges. The pieces need to be warmed up, usually to about 212°F (100°C) prior to glazing. This helps to evaporate water from the glaze slurry as it’s applied to the piece. When glazing, I pour glazes on the insides of the ware to line them and if I glaze the outsides, I spray them. Use a thicker application of glaze with a drop or two of gum Arabic added to the glaze to help with adhesion, as the body will have vitrified during the high firing. Bone China https://digitalfire.com/glossary/bone+china The process is completely different than what a potter would do: Bisque fire, glaze, high fire. Bone china is bisque fired to high fire and then glazed at a very low temperature. Since the porcelain has zero porosity, getting a glaze to stick and dry on it is not easy, the process needed goes well beyond what a normal potter would be willing to do. PS If you are not using setters, then I don't see why you cannot do a normal-ish bisque firing.

Might be worth snipping the resistor out and trying to clean it with an abrasive cleaner. PS It's a long time since I read a resistor, quick recap. Resistor Color Code Chart https://tinyurl.com/5n6ud78n A handy tool for reading resistor color code values https://tinyurl.com/5n6ud78n

... also see Power caulk gun to extruder conversion https://community.ceramicartsdaily.org/profile/894-pres/

@liambesaw You seem to be joining plastic handles to slip-cast pieces. Any comments for this thread?

Two page article (as jpegs) by Preston Rice & Madeleine Coomey ? https://1.bp.blogspot.com/-xYr-ZLHHRyc/XGsvzDufnKI/AAAAAAAAA0U/zISVLs-TKzQ3RPNKwFoc2rZ4CNnpzi3iQCLcBGAs/s1600/TT_RiceCoomey.jpg https://4.bp.blogspot.com/-6bczNxLZFgI/XGswHUKVTOI/AAAAAAAAA0c/K5DZtUz323YGyY0UNfsVDQCP0k-LhPtRgCLcBGAs/s1600/TT_RiceCoomey2.jpg From https://picworkspottery.blogspot.com/ (Pres's site?) Also as Tips and Tools: Extruder Conversion https://tinyurl.com/47cbbuv9

I don't think anybody has directly addressed this question. Understanding the Deflocculation Process in Slip Casting https://tinyurl.com/2p96x33r A simple mix of clay and water will not work well at all for casting. Not only will it quickly waterlog the molds but it will shrink too much (and therefore crack in the molds) and it will take much to long to cast. It will also gel and settle out and generally make the process miserable. Optimal casting requires that the slurry have minimal water content (e.g. 30% instead of 60%), good flow and draining properties and that it not settle out or gel too quickly. When the slurry is right the casting process works amazingly well. ... I suspect that these issues are amplified if you are trying to solid-cast.

Different methods of making handles for mugs https://tinyurl.com/yckrtf6r Video: https://tinyurl.com/mrnwfa5b

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..

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.