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GiselleNo5

Amaco dip/brush glaze compatibility issue ... help!!

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I have been using the Amaco Obsidian layered with Potter's Choice colors for some really beautiful results. I have planned a new line around this. I had been warned that the dipped and brushed glazes combined don't work well together but I forged ahead anyway because I'm clever. I purchased the bucket of C-1 Obsidian, mixed it, dipped test pieces with it, let dry for 24 hours, layered the PC over, sure enough, crawling.

I mixed some gum solution into a pint of it, brushed, layered it, normal results. 

I contacted Amaco and they have no workaround for me. They said they won't work together without the brushing gum and once the brushing gum is added I cannot dip with it. 

I know very little about glaze chemistry. Does anyone have any solution for my issue? 

 

 

 

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If you drove a petrol-engined car, you wouldn't expect it to work with diesel.

If Amaco say "it won't work", believe them.  Move on, find a different mix that will work.

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So I don't know a lot about what you are doing, but why would you wait 24 hours after applying the first coat(dip) to brush the second coat. Does it take that long to dry or something?

The moisture from the second application on a completely dry glaze will cause it to peel and crawl in my experience. Did you try brushing it on as soon as you could touch the dipped pot? 

I am not a chemist by any means, but I have found in my recent slip and glaze adventures, that if you apply layers, it must be done while the other previous layer still has a little moisture in it. Otherwise, what I think happens is that the new layer is wet and the other layer is completely dry. The dry layer quickly pulls the moisture into it from the new top layer, which means it is pulling upward away from the claybody it is on. This might not be obvious right away with glazes, but it is with slip. Thus I think what is happening with the 24 hour wait period is that when your brushing on your 2nd layer, it is pulling away the underneath layer from the clay body. Then when you fire it, of course it is going to crawl. 

Again this is just what I have observed over time. This might not be what is actually happening, but I would do something like: dip, wait till you can touch it, but it is still cool? then brush on your top layer.

I could be completely off. Someone who knows more will surely reply. 

 

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I agree with Joseph. You can't let your dipped layer dry completely before adding the next layer. This is true of dipping multiple layers, too. Doing the brushed layer sooner may not be the solution, though. The problem is that the dipped layer isn't at all durable, so when you go brushing over it you're messing up the dipped layer. When we brush multiple layers, each brushed layer has gum in it, which makes it hard and durable so the next layer doesn't affect it. Dipped glazes don't have that.

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So by Neil's logic, would doing something like spraying the dipped layer of glaze with hairspray or laundry starch help keep it from getting too messed up by a brushed layer on top?  It might not  be quite as effective a hardener as gum, but depending on what you're doing it could be cheap to try it on one pot. 

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Sounds like you might want to spray with an airbrush or something to get the next set of glazes sticking instead of brushing them. This would keep from disturbing the layer.  I don't do much dipping so I had forgotten how fragile it can be. Sprayed is completely different. Just another thought. You could also try an atomizer, though I am not sure how much extra glazes you are applying.

EDIT: Also why not dip and immediately brush while its wet? Have you tried that?

Edited by Joseph F
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1 hour ago, Callie Beller Diesel said:

So by Neil's logic, would doing something like spraying the dipped layer of glaze with hairspray or laundry starch help keep it from getting too messed up by a brushed layer on top?  It might not  be quite as effective a hardener as gum, but depending on what you're doing it could be cheap to try it on one pot. 

It's worth a try. Is there a safety/toxicity issue with hairspray in the kiln?

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11 hours ago, Chilly said:

If you drove a petrol-engined car, you wouldn't expect it to work with diesel.

If Amaco say "it won't work", believe them.  Move on, find a different mix that will work.

Right. I'm trying to find an additive or something  that will make it work. They won't ever recommend adding something to their glazes, so I've gotten all the help from them I'm going to get. I figure if there's a workaround someone here will know. 

Right now my plan is to pour the glaze layer on the inside of the cups and brush the outside so I can layer that part safely. That will take less time than brushing everything. 

Edited by GiselleNo5
Wanted to add a thought.

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1 hour ago, Joseph F said:

Sounds like you might want to spray with an airbrush or something to get the next set of glazes sticking instead of brushing them. This would keep from disturbing the layer.  I don't do much dipping so I had forgotten how fragile it can be. Sprayed is completely different. Just another thought. You could also try an atomizer, though I am not sure how much extra glazes you are applying.

EDIT: Also why not dip and immediately brush while its wet? Have you tried that?

I haven't tried dipping and immediately brushing. I was letting the dip dry overnight because that's what I always do so it will bond better to the bisque , that's what I do with brushed. It's definitely worth a try though and I like your reasoning, so thanks for the suggestion! I have noticed that same thing with slip too. I'll do a test piece the way you suggested tomorrow and see if it makes a difference. The spraying I don't have time to figure out. Plus they have to be super thickly applied or they don't show up over the black. 

Edited by GiselleNo5

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4 hours ago, neilestrick said:

I agree with Joseph. You can't let your dipped layer dry completely before adding the next layer. This is true of dipping multiple layers, too. Doing the brushed layer sooner may not be the solution, though. The problem is that the dipped layer isn't at all durable, so when you go brushing over it you're messing up the dipped layer. When we brush multiple layers, each brushed layer has gum in it, which makes it hard and durable so the next layer doesn't affect it. Dipped glazes don't have that.

 

3 hours ago, Callie Beller Diesel said:

So by Neil's logic, would doing something like spraying the dipped layer of glaze with hairspray or laundry starch help keep it from getting too messed up by a brushed layer on top?  It might not  be quite as effective a hardener as gum, but depending on what you're doing it could be cheap to try it on one pot. 

I like the idea of trying hairspray too. I have tiny test pieces I can play with these ideas. 

Does anybody know know if I can just add brushing gum to everything and dip anyway? Maybe just thin it more?? So they'll be more compatible. 

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1 minute ago, GiselleNo5 said:

 

I like the idea of trying hairspray too. I have tiny test pieces I can play with these ideas. 

Does anybody know know if I can just add brushing gum to everything and dip anyway? Maybe just thin it more?? So they'll be more compatible. 

When you add gum to a glaze, it holds more water. So if you add gum and then thin it down to dip, you'll be dipping into a glaze that has more water than a typical glaze. So if you normally dip for say a 6 count, that glaze with gum dipped for the same count won't give you the same thickness of application. So you'll have to either dip longer, assuming the pot is thick enough to take in that much water, or you'll have to dip more than once. That may work fine for the first dip, but it's not so great if you're doing it as a second dip like you are , because the pot will already be somewhat wet from the first dip, and if you let it dry completely before doing the second dip, adding that much water to the first dip will mess it up. You may be able to find a happy medium, but I think it will be imperfect and a lot of hassle even if you do get it to work.

Have you tried a different black glaze?

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The moral of this story is that there are many limitations to what you can do with commercial glazes. There is no ability to tweak them to fit your needs- they either work or they don't. If you can't get this to work, and if mixing your own glazes is not an option for you, then keep testing and hopefully you'll find something that does work. If you like dipping, then focus on testing glazes that you know you can buy in dry form and mix up for dipping. You don't have to stick with Amaco, although their glazes are great. Remember that many glazes that are kinda boring on their own can do some pretty amazing things when overlapped with other glazes. 

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21 hours ago, neilestrick said:

It's worth a try. Is there a safety/toxicity issue with hairspray in the kiln?

For the amount of starch or  hairspray that lands on the pot, I'd venture there's more burn off from the wax on the foot of the piece. I would hairspray glazed pots when I was still transporting all my work to the city arts centre. They never mentioned any problems with it, but I imagine ventilation is your friend, as always. 

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21 hours ago, bciskepottery said:

Can you also get the second glaze in powder form to mix?  That avoids the whole no-gum/gum situation. 

I don't use enough of each of them to make that worthwhile. One of them, I've had a pint for a whole year and it's got about half still in it. 

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On 10/5/2017 at 11:35 AM, neilestrick said:

Super thickly applied will also contribute to the crawling problem.

I have two pots that I glazed at the same time. One dipped in the black, the other brushed with it. I layered the other glazes over the black exactly the same thickness, and the dipped one crawled and the brushed one didn't. -.- 

I have been thinking of getting John Britt's Cone 5/6 glaze book and starting to dip my toes into the scary world of mixing my own glazes. Kinda scary at least to me since all I've ever worked with is commercial. One of the issues I've had is that I have such small chunks of time in the studio that I don't want to take up hours upon hours of that precious time with mixing and testing glazes. I've seen it take years for other people and I guess that's what I'm picturing. I don't want to take years! I want to make work now. :) 

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I am deeply regretting that I went ahead and ordered a 10 pound 2 gallon bucket of this glaze ignoring the fact that they told me this would be an issue. *facepalm* Always with the glazes, I think I can ignore everybody else's results and do my own thing. And does it go well for me? No. No, it never does. 

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The thing about using Britt's book - the glazes have been tried and trued. All you have to do is mix them up. Sure you need to test to see if they will work with your clay. But it is not like you are inventing the wheel. The heavy lifting has been done for you. Get the book and look through it. Figure out which glazes you would like to try. Get the materials needed. There probably are only a handful of materials you really need. After testing the glazes by themselves, then do what Neil suggested, layer them to see what falls out as nice. Say you have 8 glazes. Take a cylinder and divide it into 8 segments. Dip each cylinder in a different glaze. Now brush every other glaze over the dipped glaze in its respective segment. Now you can test each glaze over every other glaze.

Look at a glaze's Si:Al Ratio. The bigger the spread between the ratios the more running, streaking. For instance: Val's turqoiuse is 12.97, SH Copper Ash is 4.48. A lot of interaction going on here, a lot of beautiful streaking. Because, each glaze has something the other is lacking. Val's Turquoise has a lot of silica and a little alumina. SH Copper Ash has a lot of alumina and a little silica. BTW, I picked this tip up from reading this forum.

You can do it!

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Just to make sure I understand these parameters: the top coat of PC is crawling when applied over a heavy coat of dried Obsidian before firing? 

The Obsidian either has high boron, high sodium, and or zinc: judging from the fired gloss. 

How fast does the Obsidian dry after you apply it: in comparison to other glazes you use? If it dries much faster, more than likely sodium- as in Nep Sy.  Have you noticed any heavy particles when you sieve? 

The gum is acting like Elmer's glue in the case, tacking the top coat in place until it dries.  A fix yes, but that does not explain the reactions between the two. If the Obsidian has high Nep Sy content ( my hunch at this point) and you allow 24 hours for it to dry, then the 14-20% soluble sodium content would migrate into pockets of hydroxides. That would explain the rejection of the top coat. A thicker coat would only mean even more migration. 

One possible solution would be titration of the Obsidian. You could take an 1/8th of a cup of Obsidian, titrate it with just a couple of drops of vinegar ( lower PH) and apply to a small test tile. Wait 30-60 minutes and coat test areas with PC. 

Theory at this point, no one knows the exact chemistry of commercial glazes. But we do know how boron and  soluble salts act when we mix our own. The other fix are clay based suspenders, that act like gums. 

 

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5 hours ago, GiselleNo5 said:

I don't use enough of each of them to make that worthwhile. One of them, I've had a pint for a whole year and it's got about half still in it. 

If you are up for testing, consider letting the half pint dry out into powder, then reconstitute with water (no gum).  Then treat as a dipping glaze, like the undercoat of obsidian.

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when you say "layered the glaze over the two tests,one brushed ,one dipped in Obs. how did you layer?

one brushed?, one dipped?

if one worked I.e.brushed/brushed and dipped/ brushed or dippe/dipped th en I'd guess that you lessen your dip time, or thin your glaze.

now your dipping glaze is in soln. Test cups and measured amount of stirred glaze in each cup measured additions of water which you then can extrapolate to w ha t you need to add to your bucketful after finding the one that works

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