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commercial glaze questions


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I set up my home studio about a year ago using only commercial glazes. I have a couple of questions regarding them that hopefully you can help with.

My first question is... I love the look of a satin glaze and have used  Duncan SN351 for a while with inconsistent results. I wonder what I am doing wrong. While it's not every time or eve on every piece in a firing but some pieces comes out looking cloudy or milky :-(  Can it be the way I apply the glaze ie, brushing it on too thick or not thick enough? (I usually apply 2-3 coats) Do I not allow the glaze to dry completely between coats? Could I be applying too much pressure when brushing it on? Do I brush it too much (meaning going over it too much)? Then, I suppose something could be happening in the kiln too! Any thoughts or advice to minimize and avoid this from happening would be appreciated because whenever I use that glaze now I feel like it's a crap shoot and I don't like those odds.

My second question is about the consistency of a glaze when I open the jar. Sometimes the glazes are watery and very easy to brush on. Other times the glazes are super thick and rather dry making them next to impossible to use. I wonder what can I do to make a glaze more brush-able without compromising the glaze chemistry?  Maybe it's been sitting in a warehouse for a long time? Anyway, I've reconstituted underglazes by adding water without any problems but I wonder if that's such a good idea with a metallic glaze such as Duncan's Antique Pewter (SY1024).

Thanks in advance for all your wisdom!


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Hi Andryea!

The satin is a low fire (cone 06) glaze? What appears milky/cloudy may be tiny bubbles, which may be related to your clay, however, if not bubbles, there's "boron clouding" to look into, seeTony Hansen's article on the subject:


...the one occasion I've had some clouding (mid fire, cone 5/6), it was blotchy, in the clear glaze supplied at local Junior College lab; I had some luck with through mixing, sieving (eliminate clumps, likely gerstley borate clumps), and adjustment of the specific gravity and thixotropy (for thickness). 

Regarding consistency, should be ok to add water, however, to get the same thing each time, measure and adjust the specific gravity


and go from there, adding Epsom salt or vinegar for your thixotropy, gums or what not for brush ability. Adding water should not change the glaze chemistry at all.

Down the road, you might enjoy mixing your own glazes? Do some homework, handle the components safely, and choose wisely! Tony Hansen's reference library is a good place to start, try some of the articles, perhaps


...but be warned, you might look up to see the whole day (err, a few years?) have elapsed!


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Thanks Tony aka Hulk for taking the time to reply.

To answer your question,  yes, the glazes I'm using are low fire cone 06.

I appreciate your feedback, the suggestions and the links to all the technical information. It's a little more than my newbie brain can handle but I'm glad to have it for the future reference because... after all... who knows when and where I'll be venturing next!

Thanks again!

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@tinypieces, from the Duncan website info for the SN351 glaze they give 2 different instructions "Apply 2-3 smooth, even coats. Note the Clear Satin is only 2 coats."

I'ld try the simplest test first to see if it's an application issue. Take 6 test tiles and brush on 2 coats of glaze on 2 of them, 3 coats on another 2 test tiles and 4 coats on the last 2 test tiles. Mark the test tiles on the bottom so you know which is which. (You can use a brown Dixon high heat china marker or a ceramic underglaze pencil or an iron oxide wash with a fine paintbrush to do this) When they are dry scratch through one of each of the tiles so you can see the dried glaze thickness (wear a mask) and fire the others. See if you get the clouding more so with the 3 or 4 coats of glaze than the tile with 2 coats. (leave lots of room at the bottom of the 4 coats test tile in case it runs) If you use underglazes on your pots then do the test tiles with those also.

If the glazes brushability is okay but the glaze is super thick then it's fine to add some water. Keep good notes as you go along. Going forward use the unfired test tile as a reference to how thick the glaze should be.


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