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Hi, i’m looking for some advise / guidance on using water transfer decals. I’ve done alot of tests with mixed results with blistering. 
I have been making tiles using terracotta clay + white slip fired to 04, with a clear glaze fired to 06. The decals i have used a rubber squeegey, and paper towel or cloth to eliminate air pockets (they all look very smooth) and excess water. The latest firing was as follows:

seg 1:    50f per hour. 200f. Hold 2 hrs vented (lid ajar, peep holes open)

seg 2:     200f per hour. 800f. Hold 15 mn vented

seg 3:     250f per hour. 1200f

seg 4:    275f per hour. 1526f hold 20 mn

here are some of the results from different highs in the kiln

 

any help would be very gratefully received.

cheers, 

Ben

 

F1E70C65-11DE-48B9-8205-9AC9C16016E6.jpeg

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6 hours ago, Ben Davis said:

seg 4:    275f per hour. 1526f hold 20 mn

This seems like it could be too hot. Have you had the same problem firing lower?

I noticed your glaze is quite crazed, is this an issue for you?

Welcome to the forum. (nice to see someone from Wales, my dad and sister were born in Illanelli) 

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The glaze looks very crazed on all samples and the transfers on the right appear as if they separated around a contaminant such as silicone or oils. Were these cleaned and degreased thoroughly with a solvent before application?

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I agree that seems hot for decals-usually they are at cone 017 or 018

Now for the bubbles -use a plastic credit card or  and work from the center out in all directions or your small rubber squeegey

paper towels are not the right tool. If they have bubbles add water and try again

And as Bill says make sure they are clean. The crazing if its on the tile before adding decals can make for a non smooth surface and will make adding decals very hard as they need smooth glossy surface to work.

air bubbles can be seen when dry (use a magnifier) so do not fire them until the bubbles are gone

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The glaze firing was to 06 (mini bar) with the kiln sitter, and the glazed tiles do have micro cracks in the glaze. Would cracks in the glaze effect the decals?

I have recently purchased the kiln controller to get  more accurate firings, which is what i have used to fire the decals. These tests were distributed on all the shelves (5) in the kiln, separated by 2" shelf props. It doesn't seem to make any difference as to which shelf they were on.

I cleaned the tiles with surgical spirit (which contains castor oil and methysalicylate) which i saw recommended somewhere. I have also used just water to clean the tiles, and that doesn't seem to make any difference.

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The company who print the decals recommend 820c - 840c (1508f - 1544f) at 250c - 300c (482f - 572f) per hour with a 20 mn soak. After doing quite a bit of research it seemed to me the best approach is to have a long steady initial ramp to just below 100c (212f) to eliminate all the moisture. The timings i've used are from a Decals4Artist recommendation.

017 / 018 is around the 720c / 1330f mark.  Looks like i'm firing 100c / 212f above that. Would that cause gases in the glaze to be released ? (i've read that somewhere ??)

I'm a relative new comer to the world of ceramics, it's a lot of chemistry ! ( i am experiencing both fascination and frustration ) 

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53 minutes ago, Ben Davis said:

cleaned the tiles with surgical spirit (which contains castor oil and methysalicylate) which i saw recommended somewhere. I have also used just water to clean the tiles, and that doesn't seem to make any difference.

I am not a decal expert but am surprised at any reference to oil. My thought would be denatured alcohol or similar. I ask because the very round dots often indicate contamination with oil based products or oil residue. The glaze crazing simply means the fit with the claybody is not compatible. Likely not good for your decal application and finished piece as well but unlikely to cause the dots.

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21 minutes ago, Ben Davis said:

The company who print the decals recommend 820c - 840c (1508f - 1544f) at 250c - 300c (482f - 572f) per hour with a 20 mn soak. After doing quite a bit of research it seemed to me the best approach is to have a long steady initial ramp to just below 100c (212f) to eliminate all the moisture. The timings i've used are from a Decals4Artist recommendation.

This is very similar to a China paint application. The dry out segment is usually just a reasonable amount of time below 212f followed by a pretty fast firing temperature to the point of softening the glaze for good adhesion. 482f - 572f per hour is really pretty fast so they really are not trying to go slow by any means. As far as the top temperature I think it would be considered high for China paint  but if that is what is needed for their product to melt. I would double check their required top temperature to be sure.

Edited by Bill Kielb
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... two countries separated by a common language.

Various posters have advised "rubbing alcohol" and "denatured alcohol" instead of "surgical spirit"., but UK surgical spirit can be correctly described by both those names. While obviously containing additives that probably make it unsuitable for pre-decal cleaning.

Are methylated spirits and isopropyl alcohol  acceptable UK substitutes? (Both available on www.ebay.co.uk and elsewhere.)

 

Edited by PeterH
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46 minutes ago, PeterH said:

Are methylated spirits and isopropyl alcohol 

My vote is isopropyl or methyl for cleaning / degreasing  followed by a clean  water rinse and dry .......unless at the end of a long hard day then Ethyl alcohol to drowned my sorrows .

Edited by Bill Kielb
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The part about crazing is some is below the surface (smooth surface) and some is on top of surface (rough surface) . Only you can telll what yours is . If its smooth than teh decal will float on very well and smooth out fine-if the cracks are on the surface than I would not do decals on that surface. 

In terms of Temps-whatever the company says fireto their recomendations as they know what those colorants need to fuze well. I was specking in general decal terms which for me was cone 017 when I did lots of decal work in the 70s

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Firing the decals to the recommended temperature (1575-1650F) on an 06 glaze might mean the glaze is melting too much by the time the decal is fused on. If possible could you fire a test decal onto something that has been fired to mid or high range and see what happens? 

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12 hours ago, Bill Kielb said:

My vote is isopropyl or methyl for cleaning / degreasing  followed by a clean  water rinse and dry .......unless at the end of a long hard day then Ethyl alcohol to drowned my sorrows .

You wont see faults either after a while!

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  • 4 weeks later...

A quick report back on the decal tests....

 I successfully fired some decals on commercially made bathroom tiles, cleaned with water and a little washing up liquid, rinsed, and decals squegeed with a rubber kidney squeegee, dried for 24 hours and slowly fired to 820 centigrade (1508F).

All good. So it looks like the blistering issue is in my own made terracotta tiles (fired to 04), with clear glaze (fired to 06). Too soft ??

Has anyone got any thoughts on this, or alternative glaze firing suggestions ?

 

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27 minutes ago, Ben Davis said:

Has anyone got any thoughts on this, or alternative glaze firing suggestions ?

So just curious, were the dots the result of using an oil based cleaner or not? And if I might add, the glaze crazing was a sign of a significant difference in the fired coefficient of expansion of the clay and glaze, is the crazing intentional? Perhaps a look that you are trying to achieve with that clear glaze?

I did not notice any blisters in your original firing but that could be the pictures. We’re the round dots raised blisters?

it almost seems like you may have proved not to use oil based products to wash things off with.

Edited by Bill Kielb
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5 hours ago, Ben Davis said:

I successfully fired some decals on commercially made bathroom tiles, cleaned with water and a little washing up liquid, rinsed, and decals squegeed with a rubber kidney squeegee, dried for 24 hours and slowly fired to 820 centigrade (1508F).

All good. So it looks like the blistering issue is in my own made terracotta tiles (fired to 04), with clear glaze (fired to 06). Too soft ??

 

I don't think it's been determined if the glaze is softening too much at that temp, my hunch is it is. Since we don't have any info about the commercial tiles we can't ascertain that. Any chance you also fired one of your tiles / glaze with the same cleaning procedure? Would be good to rule in or out the cleaning methodology having an effect. One variable at a time.

 

Edited by Min
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