Salvage Operations

Hi Greg -
That's where horizontal surfaces are great - I brush a little glaze on, or just wet it with a little water and heat in microwave for a minute and then it's easy to put more glaze on the warm surface. Since many vertical pieces won't fit in a microwave, I'd heat in oven - but it's hard to fight gravity.

A suggestion was made a while back that striking makes pieces matte and the increased opaqueness hides the crazing - maybe, but the piece pictured above is as glossy as it was before striking. Striking also turns blue crystals gray. I'd love to figure that one out. I do wonder if it's from the background getting darker.

Arnie

Hi Guys,

The answer is probably in the bowels of the the old forum, but I'll ask again. My unscientific analysis is that most re-fires produce more and smaller crystals (same glaze). I would appreciate your thoughts on why this happens and approaches to avoid this, as re-fires are a fact of life, at least in my world.

Tim

Hi Tim,

Pam and I also do a lot of refires. Probably not anywhere near how many Arnie does though!
We work mostly on vertical, and I don't have an explanation for any of it, but I think it just comes down to your glaze (composition and whatnot), and your initial thickness as well as the second applied thickness. Assuming same glaze and same peak temp.

We sorta get stuff all over. Sometimes a refire will cause many smaller crystals. (Mostly we found this with our red stained pieces.) With some tweaking of the glaze we were able to fix this and now refires pretty much come out the way we expect them initially (for that glaze specifically), albeit we haven't refired that one much.

Sometimes we get the opposite. Few crystals, and spiky-er but still kinda the same size. I believe this is due to initial thickness AND reapplied thickness. being too thick. This happens with our glazes that are a little pickier with thickness. (nickel mostly.) Ive tweaked the glaze to be more forgiving but it still isnt like most of the others. I believe when this happens its too thick overall (mostly on the reglaze) because the crystals are spiky-er with the same hold temps. At one hold temp you can get a variety of shapes just off glaze thickness. But sometimes with the same glaze we can refire and get what we expect. good coverage. so it's different sometimes for the same glaze even.

Most of our glazes are pretty forgiving and we can refire expecting the same results in crystal amount, size, and shape, as an initial firing. We mostly refire Pam's mugs since most of the glazes I haven't been able to rid entirely the different color in the bg at the top when the glaze thins and since her pieces are shorter than mine she gets more of that than I do. We both like the thicker colors at the bottom so she refires and they thicken up a little and she gets more of the color she wants.
The one she finds this most with is the black glaze. That is the only one she almost fires with the intent of refiring because the first time around it usually has a lot more of the blue-ish color (though not always.) But that glaze the crystals almost always come out the same in an initial firing as they do in a refire.

We use mostly two types of clay and sometimes a third and I haven't noticed any difference between the clays but I haven't tested for it either.

When I say tweaking of the glaze to fix these issues I find it is mostly the colorants that need to be tweaked to fix it, which can be tricky sometimes to still achieve the color you want. less so tweaking of the base, but still that sometimes too.

have you tried a refired thickness test? fire a bunch of stuff in the same glaze (similar forms too). pick out three or four that all have similar results, then refire them, putting on a different amount of layers (or measured thicknesses, or grams per square inch, or however you do it) with one having no new glaze at all. see what happens.


G

I'm going to try reduction and striking after etching - but I haven't done that yet. My personal interest has been more in the area of refires, layered glazes, proportion of crystals to ground and striking and or lofire reduction. My frustration at the moment is the great difference that 1 gm of Zn makes in size and number of crystals. 21 gms is too much and 20 gms is too little - with the same firing schedule, glaze thickness, etc.
I've gotten some nice results with etching and have struck few but no full refire. I haven't paid attention to pH, and am interested in your tests.

Arnie

Hi Tom -
For post fire reduction I go up to 1350 - reduce for seven (7) minutes (!) and shut it off - and not too heavy a reduction. I started reducing for 90 minutes and through the years have kept lowering the time in reduction - am now down to 7 minutes and will be trying an even shorter time soon. Reds are much more likely to come out red - and not liver colored and blotchy. Two percent copper will probably change to the metal. I do striking to the same temp - 1350 - and hold for 90 minutes. How it all will react to acid or alkali I would like to know!
Is Copper OK to use in a kitchen, given how easily it leaches out?

Arnie