If Kiln Shelves Could Talk

I don’t know if any of you have had the pleasure of cleaning a kiln shelf in order to reapply kiln wash, but it’s one of those unpleasant but necessary tasks of a kiln owner. I recently took care of this for the first time with my kiln and learned a lot about its previous owners in the process. I’ve done this before for the kiln in my classroom, but as its a relatively new kiln, it doesn’t have much of a story to tell, and I didn’t really think about it until I began cleaning mine.

I started scraping off the old kiln wash with a putty knife which didn’t take as long as I thought it would, but I did work up a sweat. In doing so I noticed that the previous owner(s) did not know much about kilns. The kiln wash was really really thick. There were layers upon layers upon layers. Either the previous owner did not know what the heck they were doing or they were really lazy. If you put kiln wash on too thick it will more easily chip later on and or cause the shelf to have an uneven surface for your pottery to sit on. Maybe they were just lazy and didn’t feel like scraping off the kiln wash before reapplying? It was kinda interesting to see how this kiln was treated as it told me about the people who owned it and the pottery that went into it before it came to me. As I continued working and scraping I thought about how they applied kiln wash to the sides and the bottom of the kilns shelves. This is a big no-no because you run the risk of kiln wash chipping or flaking off and falling onto your pottery. If you’re firing glazed work and this happens, it’s a very effective way to ruin a piece of pottery.

As I scrape the last shelf of four I realize that this poor shelf has led a rough life. Total abuse. This shelf tells the story of why kiln wash is important. There were huge rough patches, indented and marring the surface. How did I not see this before? This happens when glazed pottery sticks to the kiln shelf. The only way to remove said pottery is to break off the pottery then use a grinder to grind off the remaining shards of pottery and glaze. You pray you don’t crack your shelf while doing this. (I did this once in Alfred. They stick you in a closet with broken shelf fragments a dust mask and a grinder to fix your mess) No wonder the kiln wash was so thick. Perhaps the previous owner did not use kiln wash, or at least not enough, then learned the hard way and overcompensated when applying it afterward? Or, they were hiding the scars like holes filled with toothpaste on a dorm room wall. Or they simply were trying to level out the shelf by filling in the potholes with kiln wash. Who knows?

All of these things kind of made me appreciate what I do know about firing pottery. I am by no means an expert, but my experience has come a long way from undergrad. It’s a cause to smile in mini celebration. If you learn anything from my experience, let it be an understanding that how you coat your kiln shelves is an important part of being a kiln owner.

Here’s what I know about applying kiln wash.

Start with a clean kiln shelf.

Kiln wash usually comes as a powder that you mix with water to your desired consistency. Find a clean container such as a bowl or glass jar. I find that pickle jars work really well for me. They’re easy to clean, have a wide mouth to reach in to stir and dip my paintbrush in, and have a lid so I can shake my kiln wash mixture. You also need a wide, soft bristled brush. If you’re intense, they make brushes specifically for this, but I find a really wide foam brush works well or my widest paintbrush. As long as it’s soft and approximately wider than 1 and a 1/2 inches across, you’re good. A wide brush helps in keeping your application even. The goal is to make the surface as smooth as possible for your pottery to sit on.

Once I have my bowl and paintbrush I eyeball the amount of water to match what I think it will take to cover all of my shelves at least twice. For me, that’s usually two inches of water in my 46 oz pickle jar. This coats four average kiln shelves. Then I slowly add about half as much of that in kiln wash to the mixture, mixing as I go. Note, you always pour the kiln wash into the water, never the other way around. Kiln wash is dangerous to breathe in in its powdered form and mixing it incorrectly or sloppily isn’t healthy for you. A dust mask is advised. Now I know my measurements are vague but really, the proportion of water to kiln wash is all about the consistency that you get in the end. I’ve looked up “instructions” but mostly what I see is the consistency, not the measurements. If you add a small bit of kiln wash at a time you won’t overshoot your consistency. You want the kiln wash to be about the thickness of milk. My test is to dip my paintbrush in the mix and lift it out. If the liquid flows off immediately in one stream, it’s too thin. If it slowly dribbles off the brush, it’s right. This is only what I do, if nervous or skeptical about my methods, I suggest you do your own research.

Once you have your proper consistency you coat your kiln shelf with a thin even layer of kiln wash. Brush in one direction completely across the shelf from edge to edge and gradually work your way across. Do not paint at random. Be methodical to get as even a coat as possible. Kiln wash tends to settle very quickly, make sure you’re mixing it up every now and then as you go. Let this first coat completely dry. This could mean leaving it overnight, this could mean running an empty kiln with your shelves in. Firing them in the kiln once would firmly set the kiln wash. Me, I let it sit for a couple hours and reapply my second coat. This is not the text book recommended method, but it works ok for me. I tend to be impatient, but if you have more patience, do one of the other methods I suggested. When it’s dry, just like pottery, the kiln shelf should feel room temperature. If it’s cold to the touch, it’s not dry. I also run my hand lightly over the surface to feel for imperfections in my brush strokes. If there are bumps, ridges, grooves or what not, I would wipe it off with a damp cloth and start over. Two to three thin coats is sufficient. They key word is thin though, you want your shelf covered but not plastered.

Like I said before, I’m by no means an expert, but maybe this will help someone out there. It’s not a complete set of instructions but it’s enough to give you a basic understanding of the process.

It was interesting for me to see the layers of kiln wash on my shelves, kinda like pulling up carpet in your home or scraping the paint off your walls. The mind of an artist is entertained by the simplest of things, haha. What does your kiln tell you? Anyone else have any stories about kiln wash?


This entry was published on January 25, 2015 at 9:41 pm. It’s filed under Uncategorized and tagged , , , , , , , , . Bookmark the permalink. Follow any comments here with the RSS feed for this post.

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