I've painted 5 coats of terra sig that's been lightly tinted with Spectrum stain onto a greenware porcelain pot. When I checked it this morning, the terra sig was flaking off. I've used this with other clays, and had no problem. I'm wondering if maybe I didn't let each coat dry thoroughly enough before adding the next coat, or could it be that the porcelain clay is too smooth? I'm new to porcelain, so don't know all it's quirks. Thanks for any suggestions.
Flaky Terra Sig
Posted 20 February 2014 - 01:59 PM
Professor Emerita Montana State University-Billings
Posted 24 February 2014 - 06:00 PM
In my past research on terra-sig, my flaking was caused from the slip shrinking at different rates than the clay... I solved this by adding
alittle of the clay body to the slip. Yes, it changes the slip to a lighter shade but only I knew it.
See you later.
Posted 24 February 2014 - 06:47 PM
Is the ware bone dry when applying the sig? It seems to help this prob if it is bone dry as terra sig soesn't shrink much on drying so maybe that's what's happenoing. I agree with Marcia, 5 coats seem a lot.
I have been making terrr.sig. by draining of the top clear layer, but have since read of others who do not throw this clearer layer out. How so you guys make your terr.sig?
Posted 25 February 2014 - 10:45 PM
Babs- do you think it is better to apply terra sig to a pot that is bone dry as opposed to one that is leatherhard?
I have been applying terra sig to my pots mostly at leatherhard. though it probably takes a few more coats. Yesterday I applied terra sig to a bone dry pot but it started cracking off. I had only put on two coats and was starting to apply a third coat when it began doing this.
Posted 26 February 2014 - 02:29 AM
No expert by far but do you really need that many coats, when the pot is bone dry it absorbs a lot on first coat, hope some expert chimes in here.
I use terra sig on the unglazed parts of my earthenware pots after i have applied slip decoration, and have only ever applied 1 coat, done on the wheel when pot is dry. .
Do what works for you as the terr. sig you're using is prob a different spec. gravity than mine... I now go by "feel" as opposed to measuring
Could add a bit more defloc. could solve the cracking prob.
Posted 11 March 2014 - 10:43 AM
I prefer to put sig on bone dry, but it has to be really watery to do so. At bone dry it allows you to burnish it without leaving marks in the clay. At leather hard it's too soft to burnish effectively, and the sig doesn't dry very quickly.
Kiln Repair Tech
L&L Kilns Distributor
Owner, Neil Estrick Gallery, LLC
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