I have done many Laser Tiles. Here is one of my best so far
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Having worked in glass clay and porcelain and compounded my own glazes your understanding seems very mixed up if the clay is barely fired then it is porus and it is at that time that glazes are applied.but they are the constituent chemicals and rarely is it âground glassâ If the glaze melts at very low temperatures ti might be used as you say, A lot of earthenware is like that. However the tiles we are talking about are not that and the glaze is there for color surface design and smoothness and nothing to do with porosity.
Earthenware bricks are porous and where freezing occurs, you can often see where the top bricks have absorbed water that then froze expanded and blown off a bit of brick. Earthenware tiles or jars will do the same.
You donât see much of it anymore but in the old fashioned Soda-Lime glass they used Manganese to hide the âcoke bottleâ green caused by iron. Under heat that manganese goes to an oxidation state that is colorless but Solar Radiation (not heat) changes that oxidation state and is purple. That glass was used on a lot of doorknobs and on the outside doors the knobs would turn purple after a few years.
in almost all the red glasses the glass is colorless when first worked but turns red when the glass is cooled and then heated. there are other chemistries that produce other colors that way. In todayâs high tech glass it can get very fancy with welding glass that goes dark in an instant and reverts back just as fast with each application choosing from an array of effects. In the case of Laser Tile they have a chemistry that does not revert back at all {though I would not leave it near an x-ray machine that might revert it) I do not know the secret of the chemistry they are using but the lasers are not used at the full force as they are with other tile, as it is the chemical change and not a damaging blow that you would be seeing.
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What an interesting conundrum. So we can tell the left tile is a fairly standard ceramic tile. available from Home Depot, Lowes and DAL Tile.
As others conjectured glaze/finish likely matters.
Out of curiosity, did you try to engrave the back where there is no glaze?
Porosity or void fraction is a measure of the void (i.e. âemptyâ) spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%.".
During firing, the porosity changes as the moisture is driven out of the clay and the voids get smaller, and thus also the body shrinks. But there is still porosity. Glazes are very low porosityâe.g. why tiles work on counters or backspashes (or sink, toilet & bathtubs), but if you put water on the underside of the tileâthe bodyâyouâll get a very different result. And why you will never see an unglazed sink for saleâŚ
BTW, Silica, which is primary component of traditional glazes, is what glass is made of. Yes, other minerals/constuents added for lowering firing temp and colors & other properties for finished item, as well as price points for that product impact âingredientsâ chosen.
And yes, earthenware is indeed much more porous than high, or hard fired porcelain (due to the type, and amount of clay vs. other components in the mix), and that has more porosity than a glaze, which will be about the same as hand blown or molded glass. And most tiles are somewhere between those⌠and the glazes used will vary, too. I was testing w/ some hand made tiles, better quality body & glaze than the the $0.11 versions from big box storesâŚ
But I agree, once seeing examples of the PhotoLaser tiles, Iâm chewing on shoe leather for my earlier statements questioning them.
I donât have nearly your experience working w/ clay & glazes directly, though I have had a handful of art studio classes working with earthen ware and porcelain, as well as studied engineering ceramics & even college projects with them (I studied materials engineering, though career focused on ferrous materials). And also years (decades now) of tiling projects in my houses w/ all sorts of ceramic, glass & stone tilesâŚ
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I could be mistaken but the 11 cent tiles (and almost all others in my possession) are hard porcelain. But as I have done a lot of ceramic and glass chemistry there is a point where the pot is âvitrifiedâ and indeed it shrinks as that air leaves, but there is usually a point that whatever holes (air) still exist will be cut off from each other and the outside.
The glaze will usually melt well below the body and be thin enough that all the bubbles will pop. Plus it will contain (usually ) less aluminum oxide that is what stiffens the clay body (usually), but a fully vitrified pot will not absorb any water even without a glaze and it is possible that both clay and glaze to have no silica at all though it would be a high temp porcelain for the clay body to be so.
Frits of ground glass are frequently used , especially with enamel and low temp glazes but I would hardly expect to see them in any mass production tile manufacturing process.
I would love to see if anyone else here has a laser tile they messed up and access to an x- ray lab to just leave it about where it would get a good dose over time and see if it went back to white. Leaving it out in the sun also is an easier experiment but could take a lot longer if it worked at all.
Many reactions reverse in radiation like the amethyst but not knowing the exact chemistry of the tiles it would just be an interesting experiment.
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Here is the stuff I was curious about:
this seems more like it works like exposing a screen printing screen. where you create a transparency and then expose through that transparency with a very bright light for 5+ minutes.
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That is very interesting for some work but under the conditions of having a Glowforge a bit less so. If you had just borax as in Twenty Mule Team Borax and a cobalt frit mixed with a binder so the fan could not blow it away the laser would melt and bind the material where it hit and the rest would wash off IMHO.
If you did not have the computer driven gadget then perhaps that would be a different matter. Then again I did just such a process by using a light fixing wax to make a silkscreen and then we silkscreened paper towels and placed them on the ceramics to transfer the design which was then fired and looked very good.
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I agree.
My immediate thought is this is another version of the old, tried and tested dichromate chemistry.
Add ammonium dichromate to any sort of protein containing solution, like gelatin, and exposure to uv or uv rich light, and the gelatin becomes insoluble in water.
If you add that sort of chemistry to a glaze, you are adding a photosensitive binder that will allow you to wash out unexposed areas, and so on.
John 
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well, the difference between that process and what weâre doing with the photo tiles is that the tiles arenât photosensitive. light doesnât affect them. when you create that gelatin and put it on a substrate, like a silk screen for silk screening, itâs now sensitive. it wonât create a screen with low light, but if you leave it in light for long, it will lose its effectiveness.
these tiles may have something similar, but iâm thinking theyâre more heat sensitive than light sensitive. or maybe some specific wavelength thatâs specific to laser light? weâre way beyond my technical capabilities at this point. i just know the process for doing the silk screening from past experience.
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Oh, alas, mistaken on those. Porcelain (kaolin clay) is expensive, and typically used only in âlinerâ tiles (e.g. 1/2" x 6" long) that need the strength for that dimension, or floor tiles (originally use was dishes/tea sets from Asiaâand not something most people could/can afford. Quite an interesting history).
And the term âporcelainâ has become so common in vernacular, itâs often used to describe types of products, and no longer really associated with kaolin clay⌠along the lines w/ Kleenex, a brand name that is now synonomous w/ any facial tissue.
The âfieldâ tiles for wall & counter use, which is what many folks have been testing with, or any other tile that you donât need a wet saw to cut, but the score/snap tool, and they may have white body, but itâs not because of the koalin content. Porcelain (high kaolin content) tiles can only be cut with a wet sawâanother reason not too common, since also more time/labor to install them.
So many compositions for tiles & their glazes, and final use and the price point dictates what theyâll be. I agree the cheaper tiles rarely have much frit if any (like the $0.11 version), or so thin, which is why itâs easy to laser thru & score & break. But many other tiles do have high silica/glass like glazes of substantial thicknessâall a matter of price point (and manufacturing process variations). Iâve always prefered hunting for a good deal on high quality things (or because I do it myself, I spend more on material since I donât pay for labor)âso my tiles are very different from what many others have.
But these photolaser tiles have some photosensitive under glaze, and a thin top glazeâso agree itâd be interesting to find out if other enery sources affect it, though I doubt at $3-4/each, natural/indoor light affects it. But Iâd not want to put any near my stove, or put hot pots on, without confirming heat doesnât affect them, eitherâŚ
Weâre getting two different processes mixed up here, I think.
Pyrofoto is a uv sensitive compound. The name might suggest the âheatâ of the laser(as in pyrography) might be effective, but thatâs a bit of misdirection.
I think itâs the association of the heat of the kiln and photography that their trying to to make.
John
As I have made a lot of porcelain I know the feel relative to talc. A key ingredient is kaolin or the âboneâ as the Chinese described it but it still needs the âmuscleâ in the right balance that would be that part that melts to hold the whole thing together, too much muscle and it does not hold up, too much bone and it does not hold together,
Good kaolin must be from rock that has weathered in place and not traveled from there where it gets mixed with other things but iron is key as that gives the red to yellow of most clays.
China obviously has the oldest sources and central U.K has a good amount but the largest sources are Central Florida that has never been the downstream of any mountains and so is extremely low in iron for both sand and kaolin.
There was a German company that set up here making concrete block and sent samples and got back a note that said in essence âvery funny, now send us the real samplesâ. so it is not so much the Kaolin that is expensive as the energy to get to cones 10-15 that fine porcelain is usually fired to.
For a longer look, there is this source that recommends a cone 5 where talc clays are frequently a cone 05 that is not vitreous and sounds it when tapped by a fingernail.
The big clay roof tiles, of course, are usually almost earthenware, and other big 18inch tiles are something else as well but when looking at the tile in my hand, a cone 5 firing looks a lot more likely than cone 05.
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Yup, and tea cup that you can nearly see through requires much finer milled & worked material than a floor tile, for example.
Hard to tell with that one, but this is an example of what I had in mind: rice bowl with translucent grains
The âgrainsâ the bowl wall is so thin itâs translucent, as can only be accomplished with high quality porcelains.
Yes, I suppose. that is an interesting trick to include rice grains while throwing the small bowl. that piece I did was about 24" in diameter when I threw it but only about 16 " out of the Kiln. the borate glaze is super thin pooling more in the lower areas emphasizing the texture that could not be touched while throwing lest it leave a mark, the piece is made 20" tall and about 4" in diameter and a wire brush run down the sides. after that, you cannot touch the outside, but it is expanded to that shape entirely from working the insides as each cut is opened up to what you see. It has to be done very slowly over several hours as-as dry as it is at the end it would break rather than expand and as wet as it is at the beginning (still very dry my most folks thinking) it would collapse.
if you put a light inside it makes a very interesting fractal pattern but I do not have a photo of that
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Impressive!
Oh, not sure the date when the rice grain pattern first started (in China)âcenturies ago, for sure, and still produced⌠And some of the saki cups w/ portraits created by varying thickness are amazing, too coming from Japan. Think Iâve seen some plaques on UK Antiques Roadshow that was from Meissen (after they perfected their version of porcelain).
An incredible media!
But have gone way off topic thread⌠sorry folks!
Things may have gone way off topic but I am grateful to everyone for increasing my knowledge.
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