Question about kiln wash shelf life

[dave laporta]

I know what your thinking ... We've answered these questions to death and I can find them in the archives. But I think my question is unique and I couldn't exactly find my answer in the archives, so here goes.

When I first started this I used the Primo wash and it worked like a charm, it went on nice and came off even nicer. But after a while it started sticking to my glass and eventually became more and more common. I got so frustrated I switched to BE wash and again got great results. While I have not experenced the wash sticking, I noticed that it became increasingly more difficult to remove the wash from my shelves. At first, it came off in nice flakes with the scrapper but now I have to really work at it. At this point I prefer the BE because I've found it has produced better results in my projects but I need to do something about removing it because this is annoying.

My questions are;

1) Do kiln washes have a shelf life and perform better when new than when it ages? (and I'm talking just months here not years) Or is it the shelves themselves? I don't know what kind they are but I have two that are yellowish and two that are more whiteish.

2) beyond the scrapping, should I wash or scrub the shelves with water or something to ensure a very clean shelf before applying new wash? At this point I just get what I can off then apply. I think I need to get them to a spotless finish for it to come off best.

3) Has anyone experienced similar situations or can offer some advice?

Thanks in advance,
Dave

[Brad Walker]

I periodically take an ordinary hand sander and thoroughly remove everything from the shelf. Wear a mask.

[Kevin Midgley]

Silicon carbide open face drywall sandpaper looks woven not a flat sheet of traditional paper. Different grits available. Use a sanding block behind the paper. Wear mask.
Aging of your mix might be occuring such that the clay, sticky hard component might be increasing. That would mean that the mix as you are using it is not being removed in an even component balance.
I haven't had problems using kiln wash that is old. The algae growing in the container must help!
Kevin

[Bert Weiss]

Dave

Kiln wash has 2 active ingredients Alumina hydrate and kaolin, and some dye. Kaolin is a high alumina clay and acts as the binder. My guess is that your ratios are changing, perhaps one of the ingredients is settling out.

[dave laporta]

So I may have a higher content of kaolin in my mix which binds to the shelf more and if I don't get the shelf totally clean this just remains every time I try remove it. Right? Then I should first throughly clean the shelves with a good sanding and mix up my batch of BE KW so that the ratios are consistant. I'll try that-

thanks Brad, Kevin and Bert.

Dave

[charlie]

a dry mix is unlikely to seperate out. are you mixing a lot and keeping it around? you might try only mixing what you need.

[dave laporta]

charlie- what I prepare may be a 12 oz. jar. Do you have any other thought of what i should try?

d

[charlie]

well, it depends upon how much you use it. i put about 4-6 teaspoons at a time in about a cup of water. that's enough for a shelf or two, and i get 2-3 firings out of each. i try to use what i make up, so save my shelves to do all at once. if i have leftovers, i let it sit, but i shake the jar a lot before using it again.

[spraydm]

I'm so glad I found this discussion, I thought I was losing it. I kept reading that Primo was so easy to wipe off but that has not been the case for me. I just came in from sanding my two shelves.

So it sounds like I am apparently mixing up too much wash (when I shake it up to use the next time it gets harder and harder to keep it from clumping at the bottom).

Also - I am confused about whether to fire only once on a kiln washed shelf or if 2-3 times is okay. I keep hearing both. And is it the same for the molds?

[The Hobbyist]

I don't know if this is any help.

I use BE KW. I premeasure and mix 4 oz plastic bottles at about 1:5 KW:water. I will make a couple dozen at a time. I use a Chicago Air Brush to apply the mix to my shelves. The KW will have settled out so first I have to shake it very well. The bottles are clear so I can tell when there is no longer any KW settled on the bottom. Occassionally there will be a bottle that takes more shaking than the others because the KW has become a little pasty. But they always spray evenly and as thick as I wish.

I always clean my shelves immediately after firing and seldom try to get an extra firing out of the shelf unless the process temp was under 1350. When I clean the shelf I scrape with a utility knife blade and then sand the surface. I sand with one hand and vacuum with the other. The part of the shelf under the glass is always more difficult to remove. The outer edges always scrape clean and need little or no sanding. Under the glass the KW is often very resistant to scraping but will succumb to sandpaper. (I'm gonna try Marty's suggested mesh.) I have noticed that the higher the temp the harder the removal. But even more so, the type of glass will make it harder. Where the glass touching the shelf was opal the KW will be tougher. French Vanilla is the worst. This becomes glaringly apparent if I fire a piece with FV and any transparent.

I never reapply KW to a mold unless I have physically damage the KW surface. I slump at 1250 so the KW doesn't break down.

As I said, probably no help at all.

Jim

[spraydm]

Interesting! So a mold will not have the same problem as a shelf does, if you do not change the wash each time? I would LOVE not to have to redo the molds.

[Brock]

Interesting! So a mold will not have the same problem as a shelf does, if you do not change the wash each time? I would LOVE not to have to redo the molds.

Yes, absolutely. You are not going as hot to slump as you are to fuse.
I used to get multiple firings out of shelves, but my molds would last years.

[spraydm]

Thank you both, that is going to save me a lot of work!

[JestersBaubles]

Interesting! So a mold will not have the same problem as a shelf does, if you do not change the wash each time? I would LOVE not to have to redo the molds.

I use Thinfire on shelves typically. I only redo my molds when the kiln wash starts flaking, which is after many firings. The problem is usually I have chipped it off during handling.

Dana W.

[Valerie Adams]

I fire 4-6 times on a shelf before recoating. I washed my molds 10 years ago when I bought them and have never recoated them.

[Morganica]

http://www.morganica.com/bloggery/2012/ ... f-scraper/

I use BE kilnwash, very much like it (except it gets everything pink and I'm not a pink fan--what was wrong with purple or aqua or orange?) Kilnwash life really depends on what I'm doing. If I'm doing a full, flat-fuse firing of a white/ivory opal glass directly on the kilnshelf, I may only get one firing out of the kilnshelf without recoating. If I'm mostly slumping or doing lighter fuses with transparents, I could use the same kilnwash for months. But typically, I scrape every month or two.

I use a wide drywall knife with a very thin blade, which gets the kilnwash off in a hurry. Then I rinse the shelf with a damp paper towel and apply kilnwash before it's entirely dried (it seems to stay on longer if the first coat doesn't soak so fast into the shelf). Every so often I go after the bare shelf with some steel wool or a drywall sanding screen to make sure I really do have everything off.

Mold-wise, again, it depends. I sometimes tack-fuse in molds, and the kilnwash usually needs to be reapplied after a couple of firings. If all I'm doing is slumping, I rarely have to recoat...but I sometimes gouge the kilnwash and it doesn't last long after that.

[Bert Weiss]

Problems can arise after kiln wash is fired hotter than the quartz inversion. This is somewhere around 1400ºF. This is why slump molds don't have problems when fusing shelves do. The quartz is in the kaolin, not the alumina.

BE kilnwash uses kaolin (a high alumina content clay) as it's binder. This is the stuff that is difficult to remove. Primo uses an organic gum for it's binder. The gum burns up and loses it's hold. Primo should wipe off. If it doesn't, I have no idea why.

I have messed around with making my own kiln washes. For slump molds, I use 50/50 alumina hydrate and kaolin (by weight) These are durable. For shelves I prefer 20 or 30% kaolin, which allows me to wipe them off each time. I should say that I seldom use hard kiln shelves, and when I do, I am firing float glass on them. I get away with a single coat of haik brushed on kiln wash. I paint on a pattern that becomes an integral part of the design. I understand that the softer glasses require a thicker layer. I use a very finely ground grade of alumina hydrate. The stuff I got at the pottery supply is not as fine and yields a rougher surface. I recommend JM Huber Alumina Trihydrate SB432.

Most of my firing is done on either fiber blanket or HD fiber boards. Both have been dusted with fine dry alumina. No wash is required. I can fire over and over with minimal maintenance. My designs utilize texture as a considered part of the package. I think minimizing texture is not only quite difficult, I prefer the textures I get.

[Bert Weiss]

I am told that the quartz inversion is actually 1063. However, practice still shows that the problems arise in the hotter firings.

The problem I am referencing is white scummy stuff on the bottom of the glass. This doesn't always happen, but is nasty when it does. A thin fresh coat is generally enough to stop it.

[spraydm]

With casting molds I clean and rewash each time. It's a pain to clean the little crevices though, does anyone have a clever way to make that task more efficient?

[Morganica]

With casting molds I clean and rewash each time. It's a pain to clean the little crevices though, does anyone have a clever way to make that task more efficient?

Depends on the size of your mold. I have a sonic dental probe I use for cleaning casting detail that also works well for this. If your mold is small (such as a pendant mold) you can probably do the same with one of those ultrasonic jewelry cleaners. Those things are fabulous.

Otherwise, if you have a pressure washer, or even one of those spray nozzles for your hose, you can use those. Be careful not to crack or chip the mold--those washers can be powerful.