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How to get glaze off of shelf

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I just bought a used gas kiln. One of the shelves has a glob of melted glaze stuck to it that I would like to remove. I have a 5 inch angle grinder I can probably grind it off with, but before I launch on that brutish strategy, I was hoping that someone could offer me a more elegant and safer solution to the problem.

 

Thanks Larry

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I just bought a used gas kiln. One of the shelves has a glob of melted glaze stuck to it that I would like to remove. I have a 5 inch angle grinder I can probably grind it off with, but before I launch on that brutish strategy, I was hoping that someone could offer me a more elegant and safer solution to the problem.

 

Thanks Larry

 

The five inch grinder will work for most cleanup after the hammer and chisel. There are also hand grinding bricks out there for the work-they take a lot of elbow grease. I use a dremel tool for small spots. Get in the habit of using kiln wash and that will alleviate most of the problems with glaze drips.

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Place the shelf on a pillow or a bag of clay. You don't want the shock to crack the shelf. I use a hammer and chisel. Goggles needed. I have a great knuckle protector on my chisel.

If there is kiln wash under this glob, you are lucky. If not, remove as much as possible with the chisel, then go to the angle grinder. If the glaze has deeply penetrated the shelf, it will re-emerge each firing. If not, just keep a heavy kiln wash on it.

Marcia

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Guest JBaymore

Personally I think for a serious glob of something nothing beats the angle grinder with a DIAMOND blade, not a masonry gringing wheel. Diamond goes thru fired clay and glaze materials like a hot knife through butter. Lots of time working in Japan with wood firing potters showed me the true wisdom of this minor monetary investment. The blades are not that expensive and last a good long while. I've been known to use the same blade to clean up wood fired work and kiln shelves and posts from my noborigama for at least a year.

 

You'll need a respriator and (impact) eye shield. Prefereably grind it outside where the dust is not such a big issue. Put the shelf on a soft support before grinding.

 

Using a hammer and chisel as well as using a rough surface masoney wheel puts a lot of vibrational stress on the kiln shelf. If there are any micro-fractures in the shelf structure, this likely will tend to exacerbate those issues. The diamond wheel is very smooth and imparts little vibration.

 

On corderite and high alumina shelves, as well as kiln posts, the diamond blade can go thru the SHELF or post quickly too. So be careful. Silicon carbide is a bit harder on the Mohs scale.... so the diamond does not eat thru it instantly.... but you have to learn how much pressure is too much there too. (My Advancers resist the diamond pretty well.)

 

best,

 

...................john

 

 

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If it is not inconvenient, could you just turn the shelf over? Put something under the blob to keep it off the shelf below, if there is a danger it would melt and fall off. Maybe it would then be easier to grind the blob off. One thing to watch out for if grinding with a carbide disk, a lot of heat is generated, which could melt the glaze and gum up the edge of the disk. Only do it in short bursts.

 

 

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John, I don't care how much it will cost, where do I find a diamond grinder for my 4" disk grinder or I have a rotary grinder that can handle up to 3/8" shanks. I even asked at a local rock shop for a diamond grinder and they didn't have the info(saw blades, yes). This would make easy work of the sometime runs, drips, and errors that plague my students work and my shelves.

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Guest JBaymore

I get my diamond angle grinder wheels at Lowes or Home Depot. I can also get them at a True Value hardware store.

 

best,

 

...................john

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Guest JBaymore

Hope you find what you need in your stores there, Larry. I am assuming that the stock in places like Lowes and Home Depot is kind of consistent everywhere.

 

I think you'll wonder why you did not find out about this sooner. I know it was a "DOH" moment for me when I made the move. I think us potters tend to have a "but that is not the way I've always done it" streak in us. wink.gif

 

best,

 

..................john

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To get glaze and kiln wash gunk off shelves, and to take the drips and chips off your ware, get a grinder that the guys who install granite counter tops use: these use rubber disks which attach to the grinder with velcro and have industrial diamonds embedded. These disks are not expensive and last a long time when run wet. They *must* be used wet because if they get hot the diamond burn away, so the grinders come with water hose attachments. Also, the water keeps the dust wet and it collects in the clay trap, instead of floating around in the air to breathe! The coarser grades (50 and 100) are great for removing errant glaze and smoothing out lumps and chips where your kiln wash didn't work. But I always use a cookie under my pieces anyway, because I work in a studio where they fire kids' stuff and there's always nasty stuff on the shelves. But if my cookie is very thin it is easy to grind it off when my own glaze combos go too runny. If a cookie sticks to the shelf it usually can be knocked off with a chisel. I have volunteered grinding the shelves and it gets them nice and smooth, but sometimes glaze has melted right into the shelf and can't be ground off, so kiln wash is necessary.

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To get glaze and kiln wash gunk off shelves, and to take the drips and chips off your ware, get a grinder that the guys who install granite counter tops use: these use rubber disks which attach to the grinder with velcro and have industrial diamonds embedded. These disks are not expensive and last a long time when run wet. They *must* be used wet because if they get hot the diamond burn away, so the grinders come with water hose attachments. Also, the water keeps the dust wet and it collects in the clay trap, instead of floating around in the air to breathe! The coarser grades (50 and 100) are great for removing errant glaze and smoothing out lumps and chips where your kiln wash didn't work. But I always use a cookie under my pieces anyway, because I work in a studio where they fire kids' stuff and there's always nasty stuff on the shelves. But if my cookie is very thin it is easy to grind it off when my own glaze combos go too runny. If a cookie sticks to the shelf it usually can be knocked off with a chisel. I have volunteered grinding the shelves and it gets them nice and smooth, but sometimes glaze has melted right into the shelf and can't be ground off, so kiln wash is necessary.

 

Also a newbie so I have to ask "What is a cookie?" 

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 Cookie. Sacrifice piece of clay, cookie shaped on which you rest any pot which is glazed with a glaze that may run and ruin your shelf or at least cost you a bit of work. A cookie can be used again and again if not spoiled. In the above firing kids work or unknown glazes this is a great shelf protector.

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I'm with John on using the grinder - in the past I've used hammer and chisel, and found that it was all too easy to make the shelf crack if the glaze was really well stuck on (I was playing with Cryolite, and drips burn half way through the shelf), so I don't need to buy any half shelves for a good while!

Don't try just turning the shelf over - even if you just use it at lower temperature firings in the future, sooner or later thermal stresses are likely to cause the stuck on glaze to break off and fall.

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To get glaze and kiln wash gunk off shelves, and to take the drips and chips off your ware, get a grinder that the guys who install granite counter tops use: these use rubber disks which attach to the grinder with velcro and have industrial diamonds embedded. These disks are not expensive and last a long time when run wet. They *must* be used wet because if they get hot the diamond burn away, so the grinders come with water hose attachments. Also, the water keeps the dust wet and it collects in the clay trap, instead of floating around in the air to breathe! .

Adding a lot of water to your kiln furniture is ill advised. Firing damp kiln shelves is like firing damp pots, except the losses are more expensive to replace. People with outdoor kilns need to protect their shelves from the elements for this reason. The notion of keeping the dust down is a good one, but sometimes just wearing the protective gear is necessary.

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So we've got a Dremel MultiMax that I use to cut 2x4s and such, rather than getting out the circular saw. I've been wondering if the scraper attachment I can get for it would do for taking off old kiln wash (not glaze drips). Anyone know if it would do the job without messing up the shelves? The particular shelves I'm thinking of are second-hand, so I don't know what kind of kiln wash mixture is on them.

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Personally I think for a serious glob of something nothing beats the angle grinder with a DIAMOND blade, not a masonry gringing wheel. Diamond goes thru fired clay and glaze materials like a hot knife through butter. Lots of time working in Japan with wood firing potters showed me the true wisdom of this minor monetary investment. The blades are not that expensive and last a good long while. I've been known to use the same blade to clean up wood fired work and kiln shelves and posts from my noborigama for at least a year.

 

You'll need a respriator and (impact) eye shield. Prefereably grind it outside where the dust is not such a big issue. Put the shelf on a soft support before grinding.

 

Using a hammer and chisel as well as using a rough surface masoney wheel puts a lot of vibrational stress on the kiln shelf. If there are any micro-fractures in the shelf structure, this likely will tend to exacerbate those issues. The diamond wheel is very smooth and imparts little vibration.

 

On corderite and high alumina shelves, as well as kiln posts, the diamond blade can go thru the SHELF or post quickly too. So be careful. Silicon carbide is a bit harder on the Mohs scale.... so the diamond does not eat thru it instantly.... but you have to learn how much pressure is too much there too. (My Advancers resist the diamond pretty well.)

 

best,

 

...................john

John,

 

Do you mean those segmented diamond dish (cup) wheels (that sound to me a way too aggressive for this purpose), "regular"  (electroplated or rigid impregnated) flat or cupped non-segmented diamond discs, diamond impregnated rubber discs or those diamond pads that get attached to a rubber backer with Velcro?  What grit?

 

Do you happen to have a photo or a link showing the one you use/like?

 

Thank you.

 

Mike

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Guest JBaymore

Like Marcia said.  The cup wheels are for "aggressive" messes.  Too much for average use.  Regular flat diamond blade for 95% of stuff.

 

best,

 

..............john

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