bciskepottery Posted June 19, 2014 Report Share Posted June 19, 2014 Is there any ingredient in the glaze (white) that could be forming crystals in the glaze bucket (e.g., tin oxide)? and have you eliminated flakes of kiln wash as a source? How is this, although the problem appear in one or two pieces ?? I've had tin oxide crystalize in a white glaze that has been sitting for a while; the crystals leave small spots on the glaze surface. Thought that might be happening, but after seeing the picture, I no longer think the tin oxide is a factor. Link to comment Share on other sites More sharing options...
bciskepottery Posted June 19, 2014 Report Share Posted June 19, 2014 In looking at reference books, the closest I've come across is a description of a "starved glaze" in Harry Fraser's "Ceramic Faults and Their Remedies". He described a "starved glaze" as a glossy glaze which lacks shine. Usually the reason is underfiring (but the cones seem to eliminate that as reason). "Sometimes only a portion or one side of an article is affected in this way, in which case the observation will usually show that the affected surface area is adjacent to a porous surface in the kiln such as a new prop column (stilt?) which has absorbed glaze vapor from the pot." His remedy is to apply kiln wash to posts. When the fault occurs to this source, it is also called "sucked" ware. Link to comment Share on other sites More sharing options...
Babs Posted June 20, 2014 Report Share Posted June 20, 2014 If it as stated only occurring in the odd pot/firing, I'd still go with lack of stirring between dipping pots. The shape of the problem area in the photo is very defined, going from base to nearly the top of the vessel. If dipping into a shallowish bucket and angling the pot to get a covering the pot may be getting into the settling sediment of an unstirred glaze. Lots of pots with blemishes, then I'd be looking around a bit more. Link to comment Share on other sites More sharing options...
Natania Posted June 20, 2014 Author Report Share Posted June 20, 2014 I generally stir the glaze quite a bit and often when dipping. Also, there is enough bentonite in the recipe to keep it in suspension. Thanks though, for the tip, Babs. Thank you also Bciskepottery for looking that up for me. I will coat the stilts in kiln wash asap since I kind of had a feeling it has to do with being too close to stilts, but not sure why I thought so. Easy enough to do. Would be wonderful if this solves the problem....! Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.