Stupid question: kiln wash

[BadExampleMan]

So, I use shelf paper under my pieces. Do I need to renew the kiln wash on the shelf before every firing?

[rosanna gusler]

no.do make sure to kiln wash the bottom of the kiln. rosanna

[BadExampleMan]

Thank you, Rosanna. How often should I renew it?

[Laurie Spray]

I use Bullseye shelf paper in every load in my Genesis. I kiln wash my shelf 1 solid layer maybe once every 30-40 firings. That in mind.....if you put it on too thick and starts to chunk off you will see those indents on the bottom of your pieces right thru the shelf paper. That is why I only brush on one layer and smooth it slightly.
I love shelf paper.....my shelf is way too heavy to move (24 x 44) and sanding it in the studio was such a pain much less kiln washing, drying etc. if you have a small shelf it is not such a big deal. On my smaller kilns with round shelves i have extra shelves and take them all outside at once, sand with a hand sander and wash. I probably rekiln wash after every few loads at full fuse or when i see areas that have come off. I never kiln wash over old wash.
I do kiln wash fresh when doing something like pot melts at 1650.
Like Rosanna I also kiln wash the floors when I have a new kiln.

[Judd]

I have found kiln wash alone is fine if I'm firing float. I use kiln wash and paper if I fire a 90, 96, or whatever kind of art glass. If I'm careful, I can get 2 or 3 firings out of the paper. I usually repaint the shelves once every 5 or 6 loads.

[BadExampleMan]

Wow, that must be a very different kind of paper than what I've always seen and used: what I use just disintegrates in the course of a single firing - nothing left afterwards but a powdery residue. No way could it ever be reused.

[Morganica]

Thinfire will lose its binder and become powdery, but if you're careful with lifting off the finished piece and laying down the new, you can actually reuse it--just don't try to move it. Thicker fiber papers can be taken in and out of the kiln for reuse if you're careful. I've reused 1/8 inch fiber paper 4 or 5 times without problem. You do have to be gentle with it.

[Laurie Spray]

I have never had success reusing Bullseye shelf paprer. It may have something to do with the fact that I use such a variety of glass in each load.....opaques, trans, 96,90 etc. although some pieces may lift off fairly clean..... Even a little uneveness will show on the back of the next piece especially if you are doing any irid side down.

[Bert Weiss]

Bad

The reason you renew kilnwash is to prevent a white scum deposit. This tends to happen after a fuse firing (not a slump firing). Considering that you are relying on the paper for a separator, you do not need to renew the undercoat. It will continue to work as a safety separator.

[Judd]

Opaques always stick to the paper. I never get a second use when using them. Iridized transparent glass is the best.

[haleybach]

Thank you, Rosanna. How often should I renew it?

This was not a stupid question, I wondered the same thing.

My first few dozen firings I used thin fire every time with kiln wash as a safety backup to protect the shelf.

After awhile the kiln wash started to flake/chip and I decided it was time to scrape and replace, since I didn't want an uneven surface under the paper.

[Bert Weiss]

Thank you, Rosanna. How often should I renew it?

This was not a stupid question, I wondered the same thing.

My first few dozen firings I used thin fire every time with kiln wash as a safety backup to protect the shelf.

After awhile the kiln wash started to flake/chip and I decided it was time to scrape and replace, since I didn't want an uneven surface under the paper.

When your build up of kilnwash gets to a certain point, it begins to flake and chip. This is why I recommend not renewing it every time when you are using paper over it.

Fusing directly on kilnwash is another thing all together. It doesn't take a dense overcoat to avoid the white scum thing. I make my own kiln washes and when I know that I am going to remove it, I usually use less kaolin (china clay), so it comes off easier.

[JestersBaubles]

I use ThinFire or Papyros but never kiln wash my shelves. Heck, if I'm gonna use kiln wash in the first place, why would I waste the paper?

Supposedly, the Papyros can be used multiple times, but I haven't so far. The biggest advantage I see is that it cleans up easier than TF (stays in one piece if you carefully fold it with a spatula and then scoop it out).

Dana W.

[rosanna gusler]

I have ruined a kiln shelf by fusing on fiber with no kw underneath. Kiln over fired and glass went through the fiber and is permanently bonded to the shelf. R.

[haleybach]

When your build up of kilnwash gets to a certain point, it begins to flake and chip. This is why I recommend not renewing it every time when you are using paper over it.

Fusing directly on kilnwash is another thing all together. It doesn't take a dense overcoat to avoid the white scum thing. I make my own kiln washes and when I know that I am going to remove it, I usually use less kaolin (china clay), so it comes off easier.

I spent way too long scrapping shelves this weekend. Maybe I have too many shelves.
I've only been working with glass for a few years and only with my own kiln a very short while. I have 'figure out this kiln wash thing' on my short list of things I need to learn.

By 'less kaolin' are we talking 25%, less? More?
Have you tried calcinated EPK like potters use in their bat wash (25% Calcinated EPK, 25% EPK, 50% alumina hydrate)?

Also do you add anything to keep it from settling out? I'm thinking a tiny bit of bentonite might do it, but not sure if this is a bad idea. I know I can just add marbles and shake.

If you know you are going to remove it (I assume because you are going to full fuse temps) are fewer coats ok? I'm not clear on if the 5 coat thing is for a)durability b)smoothness or c)to assure good coverage.

I'm highly experimental with most of this glass stuff, but I ruined one shelf early on and have been a bit gun shy ever since. I don't need any more dams at this point!

TIA,
Haley

[Bert Weiss]

When your build up of kilnwash gets to a certain point, it begins to flake and chip. This is why I recommend not renewing it every time when you are using paper over it.

Fusing directly on kilnwash is another thing all together. It doesn't take a dense overcoat to avoid the white scum thing. I make my own kiln washes and when I know that I am going to remove it, I usually use less kaolin (china clay), so it comes off easier.

I spent way too long scrapping shelves this weekend. Maybe I have too many shelves.
I've only been working with glass for a few years and only with my own kiln a very short while. I have 'figure out this kiln wash thing' on my short list of things I need to learn.

By 'less kaolin' are we talking 25%, less? More?
Have you tried calcinated EPK like potters use in their bat wash (25% Calcinated EPK, 25% EPK, 50% alumina hydrate)?

Also do you add anything to keep it from settling out? I'm thinking a tiny bit of bentonite might do it, but not sure if this is a bad idea. I know I can just add marbles and shake.

If you know you are going to remove it (I assume because you are going to full fuse temps) are fewer coats ok? I'm not clear on if the 5 coat thing is for a)durability b)smoothness or c)to assure good coverage.

I'm highly experimental with most of this glass stuff, but I ruined one shelf early on and have been a bit gun shy ever since. I don't need any more dams at this point!

TIA,
Haley

I've tried liquid CMC and alumina, but it sinks in to the shelf, oddly, and not evenly. Some EPK seems to help how this works. I never heard of calcined EPK. I have heard of calcined alumina. It has been heated quite hot which removes the chemically attached water. This is a good thing, but not necessary. I think calcined alumina costs less in Australia than it does in the USA.

Like many glass related recipes, there is a wide range of what works and you can tweak the recipe to work better for you. 20% EPK can be removed with a paper towel or drywall sander.

The thickness of your application is determined by what sort of glass you are firing and to what temperature. Float just needs a thin layer, and white opals, fired hot, are the biggest challenge.

I find that kilnwash reconstitutes really easily with water and a stir or shake. It does not tend to clump, so I have no need to worry about keeping it in suspension. One of the big deals is whether you choose to mix your kilnwash to the consistency of cream or skim milk. I am a skim milk mixer.

My messing around has shown me that the most important factor is the grind of your alumina hydrate. I love the finely ground type I use. I have settled on using 50/50 on my stainless steel slump molds, and 80/20 on my mullite shelves. However, most of my work is done either on powdered blanket or a sand mixture. The same finely ground alumina is used on both.

[haleybach]

Excellent, thank you.

EPK is wonderful stuff, I hope there is a good supply!
Where do you get finely ground alumina? My pottery supply doesn't even specify a mesh.

[Bert Weiss]

Excellent, thank you.

EPK is wonderful stuff, I hope there is a good supply!
Where do you get finely ground alumina? My pottery supply doesn't even specify a mesh.

If you live in the northeast, the distributor for it is M. F. Cachat in Ohio. I think they cover south to Maryland, and west to Denver. I do not know the other regions of the US. The product is made by J.M. Huber and is called SB432 Alumina tri-hydrate.

I started out with a different company's product, but that company ceased to provide it. I was lucky to find a distributor I drove by, and bought enough to last me for a very long time. I'm running out now. Shipping likely doubles the cost.

The difference between the finely ground and not finely ground, is dramatic and significant. And, BTW, one person reported getting a much finer version than the one I use, and she reported white scum problems with it. So, there seems to be a sweet range.

[haleybach]

Thanks!