etching reacted to Dick White in Plaster Moulds Transfering Layers Of Plaster Onto Clay
Agree with Nerd - logically, it isn't a problem with a change in the plaster mix as some older molds started exhibiting the behavior at the same time. The only thing that is new is the slip. As Nerd suggests - a change in the slip supplier if commercial slip is being used, or change in the recipe if mixing one's own slip. If it is a pre-mixed commercial slip, there could be a manufacturing change that is not published. For self-mixed recipes, there is a possibility of a change in the water. If on a well system, is there a water softening system that the filter was recently refreshed? If on public water, did the utility start using a different conditioner.
etching reacted to glazenerd in Plaster Moulds Transfering Layers Of Plaster Onto Clay
Something troubles me about this particular circumstance. All the molds started doing it at the same time; some new, some several years old.
1. Have you changed slip supplier or recipe?
2. Did you recently store household chemicals nearby? ( looking for acids evaporating)
3. Did they freeze and thaw several times?
etching reacted to Marcia Selsor in Plaster Moulds Transfering Layers Of Plaster Onto Clay
did you mix the plaster yourself? could you have added too much water in the mix? I think the plaster is breaking down. Is it possible there is sonething in the slip you're using? If the plastic clay doesn't cause a problem , it is likely the slip you are using.