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docweathers

Brushing Glaze Smoothly

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docweathers    79

I usually spray on glazes. Recently, I made some shapes much too complicated and restricted to get even an airbrush in position to spray. The only alternative I can see is brushing on glazes.  However, my glaze brushing looks like a four-year-olds fingerpainting. Can someone explain how to get very nice smooth glaze application with a brush, or point me to an article that lays it out.

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firenflux    45

The key for me is to stop my brush stroke and reload before the brush is dry. You also need to use the right brush and make sure your glaze is formulated for brushing. A brush with softer bristles is best. it does take practice like anything to do with making pottery. I also know that the way I brush glaze on, certain glazes need 4 coats instead of 3 so they don't come out blotchy.

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I use those thick bamboo brushes that're used for wide sumi-e and Eastern calligraphy. The glaze goes on so well and the brush covers a wide area, so time is saved quite a bit. :3

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Chilly    329

What cone are you using ?  I find that higher temperature glazes are harder to brush, but discovered that adding a few drops of glycerine to the glaze helps.

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Celia UK    142

I mostly use transparent, glossy glazes and I've found that even though some don't brush on smoothly, they even out very nicely in the firing, even at low temperatures.

Brushing over with a soft brush and finger sanding the dry glaze will smooth out the worst irregularities (if you can reach them!)

I've also added glycerin, which helps by slowing down the drying time. If you use this, I'd advise against tipping it back into your main bucket, as it tends to grow mould.

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Marcia Selsor    1,301

Celia is right. Yes, glycerin and there are commercial "brushing" additives available which are probably glycerin.

 

Marcia

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docweathers    79

What do you mean that "the glaze has to be formulated for brushing"?

I'm firing at cone 6 oxidation

In the right brush, what parameters do you look for?

Is there any reason to believe that brushing additives do any better than glycerin. I've tried glycerin. It seems to help a bit, but I'm not impressed.

 

Has anyone tried V-gum or CMC to make the glaze more brushable?

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Celia UK    142

Paul - Around 10% as an estimate. Try a small sample and see how it feels.

 

Doc - I have these notes about CMC gum.

Powdered gum resists dispersion in water thus it is difficult to add it to an existing liquid batch. However if gum powder is mixed with other dry ingredients before adding them to the water it can be done (often 0.5-1.5%). A much more effective method is to boil water, add about 25-30 grams of powdered gum per litre and mix vigorously with a mechanical mixer. Normally this mixture is added during mixing to replace part of the water however I have found that for brushing it should be used to makeup the entire water complement. There is room to use 40 grams per liter if needed.

 

CAD 14/2/15 Neilstrick

For brushing:

Add 2 tablespoons CMC Gum to a gallon of water. Add 1/4 teaspoon copper carbonate as a preservative, otherwise bacteria will eat up much of the gum within a few days. It will not affect the color of the glaze. Let it sit overnight, then blend with a hand blender. When making your glaze, substitute the gum solution for about 1/3 of the water.

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firenflux    45

Formulated for brushing means it has the additives like Celia posted above. If it doesn't have those the glaze is absorbed by the pot too quickly and will not brush on smooth.

 

For brushes, it's more a personal choice. I like the soft bristled synthetic ones. Fan brushes in particular I found do a large area with little glaze waste and brush on smoothly. For smaller areas I like the cheap bamboo brushes.

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oldlady    1,323

wet the greenware before trying to brush anything on it.  just dunk it in a bucket of water, it is surprising how little water it takes to make the piece not act like it has been in a desert for a week.

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flowerdry    128

Oldlady, you mean bisqueware, right?

Commercial brushing glazes directions usually advise to brush each coat in opposite directions....but I have never done that and get good results anyway.  Having done a lot of brushing, I've found that some glazes come out better than others.  Some I need to be meticulous with, and others come out good now matter what I do.  My best advice is don't try brushing a glaze that is too thick, thin it down with water, work quickly, and be sure to let each coat dry before applying the next one.

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Bob Coyle    113

Brushing on glaze does take practice. I brush all of my glazes and have great difficulty in teaching the technique in class. I use a four section Sumi brush and try to FLOW the glaze off of the brush instead of painting it on. By flow I mean never let the brush starve out and go dry. This means loading it up fully till it almost drips and immediately brushing it on the piece till the brush starts to run out of glaze. You need to go fast and keep a wet edge. you can be a little sloppy and come back and brush over the runs and drips later.

 

I am usually able to to keep the whole piece moist enough to cover it with a full coat before it dries. I can then FLOW another coat over the first and even out the rough spots. The key is to keep the brush totally saturated with glaze and  go fast enough so that you keep a wet edge between brush strokes. The big mistake people make is brushing on too thin. That is why four coats are required to do the job. I never use more than one thick coat and a second touch up on the thin areas. I tell my students to put it on till it looks way to thick, and then it is about right.

 

I formulate my own glazes and keep them at about 60% solids. The thicker the better for brushing. I add 1% brushing medium (CMC + perservative) to help stick it to the pot and smooth the brushing.  I weigh out the brushing medium and add just enough alcohol to get it so it is soluble, and swishes around on the bottom of the cup I use. I then quickly add this to the water I use for the glaze and wash the cup and water back and forth . I find this prevents the gum from clumping when the water hits it, and I don't need to use heat or high speed mixers to get it dispersed through the glaze mix.

 

I try to mask parts of a piece I don't want to glaze and just slop it on rather than use small brushes around tight areas. I use latex masking that pulls off and seldom require touch up around the masked areas.

 

As Cilia said, the glaze tends to level in firing, and if I have applied it heavy enough I don't get brush marks.

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docweathers    79

thanks for all useful suggestions. As I have been experimenting with them, it also seems helpful to flocculate the glaze with Epson salts or calcium nitrate.

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oldlady    1,323

thanks, doris, i fixed it with "edit".  a late night after a long day................... -_-

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