Kiln Wash Won't stick in mold

[Ross Mayfield]

I have a new ceramic mold and the BE kiln wash will not stick to one small spot. I even tried leaving a thin puddle over the spot when I baked it, but no good, it came right off. What should I do to make it stick?
Hopefully, Ross

[Jerry]

It's hard to know what's going on without being there, but it sounds like there's something on the mold keeping the wash from sticking. From time to time I'll get careless with wax and get it places I don't want it and it behaves the same way. Not suggesting you are careless, but there could be any of several products that got splashed on your mold and the wash won't stick. I suggest using steel wool on the mold, especially that spot and trying all over. If you can get down to the bare ceramic material there's no reason the wash won't stick.

Good luck,
Jerry

[Brad Walker]

I have a new ceramic mold and the BE kiln wash will not stick to one small spot. I even tried leaving a thin puddle over the spot when I baked it, but no good, it came right off. What should I do to make it stick?
Hopefully, Ross

You probably don't have to do anything. It's common for ceramic molds to have a spot where the kiln wash doesn't appear to go on properly. It will usually look a little whiteish, but should work just fine.

[Gil Reynolds]

I agree scuffing that area might help or you may try firing the mold to 1100F to burn out possible contamination. Another trick to try is heating the mold to 200F and spraying the kiln wash onto that spot. Avoid heating above 200F because hotter ceramic molds can crack when sprayed with the cold kiln wash.
Best of Luck
Gil

[Cliff Swanson]

I had the very same issue when I prepped my first ceramic mold a few months ago. There is a fair amount of discussion of this issue in the archives, but basically those spots are places where the ceramic is of a different character and density than the rest of the mold. Ditto with Brad... Nothing need be done about it, as it seems that the glass would have to be taken to much higher temps than are normal for slumping before sticking might occur. I've successfully slumped onto a mold with this condition and the pieces have not stuck.

Cliff

[Ross Mayfield]

As usual the board has come through. This is the first time I have experienced this in a little over 18 months of doing glass. Thanks to all.
Happy Ross

[lohman]

The mystery of why one spot on your ceramic mold won't take kiln wash has a very non-mystereous solution: Many ceramic molds are made by slip-casting which involves pouring liquid clay (slip) into the plaster molds.
When the pour is being done the stream of slip falls on the same spot on the mold and the clay particles pack themselves a little denser than the rest of the body of the mold. This creates a spot that is harder than the rest of the piece and therein lies the reason why your wash doesn't stick.
The advice already given in sound.