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Corn Starch and Reglazing


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So I pulled a few pieces from my last firing that were super underwhelming. I have been thinking about trying to re-fire them just because I haven't tried it yet and it's only a few pieces so not super time consuming. I've read everywhere about heating pieces, hairspray, starch spray, etc. I first heated the pieces and then dipped them. When I went to clean off the bottoms, the glaze inevitably smeared off where my fingers were. My thought was to maybe use spray starch all over the already applied first layer of glaze and then paint on another layer of 2 of glaze. If I already have a layer of glaze underneath the starch spray - will that cause any problems in the firing? All I can picture in my head is the glaze just totally oozing off the pot in the kiln haha and I would like to avoid that! 

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When refiring pieces that you want more glaze on =

Get them warm then spray or dip them into glaze-let dry completely before handling 

handle them as little as possible -get the glaze off bottoms.

I have been in a full time ceramnics profession for over 45 yaers and never used or own hairspray 

to answer your question it will just burn off and not cause you issues most likely-but you do not need it

if you want more glaze layers just warm the work and reglaze-let dry and do it again until you have enough glaze.

 

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I JUST tried this with some pieces, know just how you feel.
I was trying to salvage some cups that had crazed - would have just thrown them out but I'd spent a lot of time on an exterior detail and hope springs eternal. 

Unsuccessful Tactics
I tried laundry spray starch and hairspray - neither worked for me.
The glaze kind of stuck to the spray in a patchy way, kind of like when a soup with dairy will form a skin as it cools,  and then it moved around unevenly on the surface, sliding down the sides. 

Tried heating my ware in the oven to 175 degrees and dipping, the layer of glaze that stuck was way too thin.
When I tried reheating and adding a second layer, the first layer came off in places, dripped funnily, and made a mess. 

Successful 
Using commercial brushing glazes actually worked well - they are much thicker and stickier than my own glazes (and probably a little dehydrated, to boot). I was able to add multiple layers - took a very long time to dry, hours, but it worked and did not come off or drip. 

Outcome
While I didn't like the way the refiring came out (I only had a few old glazes I had stopped using for a reason) theoretically, if I'd had a clear or better color, it might have worked. The application was fine and the new glaze fused with the existing glaze and corrected the crazing, I just didn't like the way it looked. 

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5 hours ago, kristinanoel said:

I JUST tried this with some pieces, know just how you feel.
I was trying to salvage some cups that had crazed - would have just thrown them out but I'd spent a lot of time on an exterior detail and hope springs eternal. 

Unsuccessful Tactics
I tried laundry spray starch and hairspray - neither worked for me.
The glaze kind of stuck to the spray in a patchy way, kind of like when a soup with dairy will form a skin as it cools,  and then it moved around unevenly on the surface, sliding down the sides. 

Tried heating my ware in the oven to 175 degrees and dipping, the layer of glaze that stuck was way too thin.
When I tried reheating and adding a second layer, the first layer came off in places, dripped funnily, and made a mess. 

Successful 
Using commercial brushing glazes actually worked well - they are much thicker and stickier than my own glazes (and probably a little dehydrated, to boot). I was able to add multiple layers - took a very long time to dry, hours, but it worked and did not come off or drip. 

Outcome
While I didn't like the way the refiring came out (I only had a few old glazes I had stopped using for a reason) theoretically, if I'd had a clear or better color, it might have worked. The application was fine and the new glaze fused with the existing glaze and corrected the crazing, I just didn't like the way it looked. 

Thank you SO much for your response. I really appreciate you laying it out the way you did and being so thorough.  Bummer that you're re-firing didn't come out how you wanted! Those finicky kiln gods.

I tried the heating method also and was really disappointed with the results. The glaze was so thin and it was literally impossible to handle even to wipe off the bottoms because it just smudged off in my fingers leaving blank spots. 

I made a homemade corn starch spray by warming 2½ cups water with 1½ tbsp corn starch, bringing to a boil and then letting cool. I sprayed the pieces all over and it worked remarkably well! The glazes really stuck to it after I let it dry on the pieces. And they also did not smudge at ALL when handled. As long as the re-firing is successful then I think this may be a good method! 

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Just now, kristinanoel said:

Glad to hear you were successful!

And what kind of device did you use to spray your cornstarch mixture? 
Are you using a spray gun/air compressor?
Just a regular spray bottle? 

 

I put the starch spray in just a dinky plastic spray bottle and then painted on the glaze.  It definitely took longer to dry between layers than normal glazing but nothing crazy. 

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13 hours ago, Kktbs23 said:

If I already have a layer of glaze underneath the starch spray - will that cause any problems in the firing? All I can picture in my head is the glaze just totally oozing off the pot in the kiln haha and I would like to avoid that! 

If you don't know how refiring is going to effect the glazes it's a good idea to fire them on a thin waster slab of clay to catch any possible glaze runs. First glaze has already melted so refiring it can make it more fluid. Waster slab doesn't have to be bisque fired first, just make sure it's really dry. Another thing you might want to consider is placing the reglazed pieces in a cooler spot in your kiln. Some claybodies (especially porcelains and smooth stoneware) can bloat when fired a second time due to the body being fired with the extra heatwork. Refires are always a crapshoot but if there is nothing to loose worth a go. 

Welcome to the forum!

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9 hours ago, Min said:

If you don't know how refiring is going to effect the glazes it's a good idea to fire them on a thin waster slab of clay to catch any possible glaze runs. First glaze has already melted so refiring it can make it more fluid. Waster slab doesn't have to be bisque fired first, just make sure it's really dry. Another thing you might want to consider is placing the reglazed pieces in a cooler spot in your kiln. Some claybodies (especially porcelains and smooth stoneware) can bloat when fired a second time due to the body being fired with the extra heatwork. Refires are always a crapshoot but if there is nothing to loose worth a go. 

Welcome to the forum!

Thank you!! I'm always in awe of how willing to share knowledge anyone in ceramics is. If I don't have any of the thin slabs, would it work to put old bisque fired pieces under them that I have no intention of using? 

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3 hours ago, Kktbs23 said:

If I don't have any of the thin slabs, would it work to put old bisque fired pieces under them that I have no intention of using? 

Yes. 

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To further what @kristinanoelsaid about commercial glazes sticking better: they work better because they have gums and other brushing mediums in them so that they go on more smoothly.  If you have some CMC gum, or glycerine or some extender that they sell at the paint store, adding a little of that to some of your dipping glaze may work better than trying to get an unaltered glaze to stick.

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I have waited until I have a kiln that is still warm, then put the pieces to be reglazed in there for a time.  Then I use gloves to take them out and redip or re spray them.  That has worked fairly well.  I have a small square heater that is a workhorse.  I have put the pieces in front of the heater until the piece is pretty dang hot and then re dip .  That has worked.  But not always. Depends on the glaze and the clay and the phase of the moon! :D

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I have poured off (and saved to return to the mix) the liquid from the top of the glaze (yes, I am losing some dissolved chemicals) then dipped heated pots into the thick glaze.  It works to some extent.  Lin

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