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Jul 12

Mar Sara flakiness

in Watertown Discussion

Hi folks! I adore mar sara as one of my favorite stable glazes, but lately I cannot seem to apply it without it becoming too flaky to be fired. I’ve tried doing a super fast dip & applying by brush but still ended up with flaking; putting it as the first coat in a combo or a second coat also didn’t seem to change anything. Is it just me? Any tips to combat? Thanks!!

6 comments

6 Comments

Stephanie Morrison

Jul 18

Ned, A semi-related question but for Umoja: will it come back from its time-out? I remember there were flaking issues on that one, maybe similar or different from Mar Sara, and it was such a favorite. Thanks for the BTS of glazing chemistry/sorcery.

Ned Levering

Jul 18

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Replying to

Omg. Funnnny you mention Umoja. This is a quote from Jared in our slack channel, "I haven’t wanted to speak it into existence but Mar Sara has been behaving very Umoja like and it’s scaryyyyy" Haha.

Sadly, I'm not sure if Umoja will every come back. We never changed anything about Umoja before it become un-usably flakey which was very mysterious. The likely cause is a materials substitution. Suppliers shop around for materials like clay, feldspars and frits.

The good news is for Mar Sara is actually that it has a history of being flakey in it's early days, so we have a good idea of possible ways to fix it. Not the case with Umoja. But seriously...don't compare it to Umoja too much or it might happen 👻

leilamegs

Jul 17

Thanks so much for the update Ned! The technical side of glaze stuff is so fascinating (and mysterious haha) to me!

Just wondering if you have a sense of whether this is a short term vacation for mar sara or more indefinite? Sorry to ask, I just have a project I’m trying to finish in the next few weeks that I had planned to use marsara on so just trying to get a sense of whether I need to pivot!

Thanks again, appreciate yall!

Ned Levering

Jul 17

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Replying to

Hi! We're mixing a new batch this week with adjusted materials. It probably won't be mixed, tested and ready for use until Monday of next week I'd guess. We're waiting for calcined bone ash to come out of the kiln today.

Ned Levering

Jul 16

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!Update! Hi Leila - you were completely onto something here! Jared came back from vacation yesterday and told me the Mar Sara has been behaving wayyyy worse than normal and flaking. It's been pulled from the floor in Watertown. The source of the problem in this case is a materials one. The industry stopped producing Glomax. It's a calcined form of kaolin (meaning it's already been fired in a kiln once) and so helps with shrinking behavior on application. We made a substitution with regular EPK and reduced our bentonite addition, but it clearly made a problem. We're working on a fix. Stay tuned. Thanks. Ned

Ned Levering

Jul 13

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Hi Leila! Mar Sara is also one of my favorite glazes :) It sounds like you're already doing the right things to help with flakiness/crawling. In general, a thinner application is less likely to flake. If a glaze is prone to flaking, it usually coincides with gathering thickly on the pot during application. You also want your glaze layer to dry quickly after application. For flakey-prone glazes, often the first layer appears to dry instantly. Underneath that glaze layer though, the clay is still saturated with water. This means the second layer will sit on the pot for a long time without drying and this almost always leads to flaking. So don't be tricked into applying the second layer of glaze too soon! Waiting 30-45 mins instead of the typical 10-15 can help.

Flakey-prone glazes usually don't require two full dips. I like to do 1.5 layers, which means I dip the pot in the glaze quickly, lift it out, wait about 10 seconds and then quickly dip it again. I've been doing this for years with Mar Sara and consistently get the tomato red I'm looking for.

If a glaze is prone to flaking, you should really only consider layering it with a second glaze that is known not to flake. Flakiness comes from certain glaze materials that swell with water (the main one being clay). The studio glazes that are known to sometimes flake are:

Satin White
Mar Sara (less so)
Dehaka Purple
Neo Steel
Thermal Yellow
Assad Black (less so)

I'm also a believer now that flaking is a semi-seasonal issue that worsens in the summer. It must be connected to the humidity. Just this year we started making minor adjustments in our glaze bentonite additions to counteract it.

Hope this helps!

Ned