Tag Archives: salt firing

In Praise of Wadding…

Without wadding, there would be no salt firing.  I believe that most atmospheric firers wad their pots to some degree, and I know that there is great variation in how wadding is made among potters.  For those of you who have not taken part in salt firing of pottery or other atmospheric firing, the vaporous kiss of the salt (or wood ash, or soda….) is what creates the special effects we seek on the surface of our work.  That same vaporous kiss will fuse your pot right to the shelf upon which it sits, where it may shatter into dangerous shards as the kiln cools and it cannot shrink at the same rate as the shelf.  What to do?

Each piece that goes into the kiln must perch upon balls of wadding.  This wadding leaves small white circles where it has been adhered to the pot.  Many buyers hate these white dots, and want pots that don’t have them. They are particularly incensed by the wad marks – usually long ovals – that remain from where wads are placed when casserole lids are fired in place.  Sigh…  Here are some typical wad marks on a salt pig from my recent load.

Salt Pig 1 Bottom

I have used a lot of different combinations of materials to make my wadding.  At this time, I use a 50-50 mixture of alumina hydrate and Helmar kaolin BY VOLUME.  Wearing my respirator, I measure the materials out into a plastic dishpan.  I use about 8 cups of each material, which makes about 10 pounds of wadding.  I mix the two materials by hand, and then add water.  It’s okay to make it too sloppy; just add more of each until you get it right.

I like to make wadding one batch ahead during a firing.  That way, it has time to become more plastic and easier to roll out into coils.   I often mix up the wadding, and then cover it with plastic for a few days before wedging.  I prefer to wedge it on the formica top of my slab roller table rather than on my plaster wedging table.  The alumina hydrate makes it into un-clay, and it sticks to the plaster in an untidy way, even as it is being blended.

When it is smooth and uniform, and still a bit wetter than I would like when I make my wads, I pack it into a tightly covered plastic container from the restaurant supply store and put it in my storage area.  It’s good to keep it on the wet side, because unlike clay, I can’t seem to rehydrate it by spritzing or sprinkling water into it.  Other wads have been easy to rehydrate, but this wad has specific properties that are more important.

What are the properties a salt-firer requires from wadding?  First, and most important, is how the wadding comes free from the pot after firing.  The first wads I used required much hand sanding to make the places where wads had been adhered smooth and attractive.  This quickly becomes wearisome!  I have been known to describe myself a a connoisseur of abrasives, and this is sadly true.  Shelves must be sanded after each firing, kiln posts too; you have to be a little bit nuts to do all this work when you could snatch soulless but serviceable cone 6 pots out of an electric kiln with none of these annoyances…

My first hands-on experience with salt firing was as observer of Craig Martell’s salt-firing process.  Craig has a big salt kiln that he fires occasionally, and agreed to let me come when he was setting up to fire, and even put some of my first pots for salt in his kiln.  I helped with wadding, and learned that a person has to stick the wads on with Elmer’s. Craig has vast technical knowledge, and without his help, I would have given up on learning to salt fire and returned to red earthenware, most likely.  Here’s a pot of mine from that firing in Craig’s kiln. I have never been able to duplicate some of the effects on this humble piece – I still use this gold slip, but it hasn’t been willing do this in any of my three salt kilns….

Pot from CRaigs Kiln

The first wadding I made myself incorporated flour along with alumina hydrate and EPK kaolin.  It was okay to roll out, made decent balls/spheres/bollitos of wadding.  It also soured quickly and needed to be used with a day or two.  I used to put the leftover bits of wadding into the freezer, and still find a small,  mysterious bag of frozen dough once in a while.

James Tingey, another fine Oregon potter, came up and fired with me once,  and introduced me to wadding made with wood sawdust.  This took less sanding, but made a larger minimum wad which didn’t work for my small pieces such as butter boxes.  I am not sure at what point I switched to my present mix, but it’s clearly the best for ease of forming and removal, and keeps forever.  It becomes much more plastic as time goes on, too.

There are two principle uses for wadding in the kiln; setting up the pots, and wadding the furniture.  I may also use wadding for chinking in the kiln, especially since I am laying up a brick door again.  It shrinks, and probably doesn’t really stop that much flame, but it makes me feel like I am doing something.  Better to stuff shreds of kaowool in; but I worry about fibers.  I should research this hazard…

I like to make all the wads for the firing before I start stick them on, and have become surprising good at guessing how many will be needed.  I need two full plates of 1/2″ balls for general use, about 100 3/4″ balls for wadding the contact point between my silicon carbide barstock and the shelves, and about 32 big fat wads of wad for the tops of the posts I use top separate the shelves – 4 per shelf.  Here’s a plate of small wads ready for wadding pot bottoms and lids as well.  I fill up rectangular plastic plates, which are tucked into ziplock bags.


Potter friends contact me from time to time to tell me about new ways to make wads.  A potter somewhere rolls wadding into a small slab, then presses a straightedge into the slab at intervals, in two directions, to create small regular cubes connected at the base,  It’s bisqued, snapped apart, and glued onto pots.  Is this easier than what I do?  Maybe…

How does a potter learn this stuff?  I have been extraordinarily well mentored, not only by Craig, but also by longtime friend and ceramic engineer Barrett Jackson, who regularly introduces me to all sorts of high tech materials.  From him, I got boxes of ceramic cam rollers – diesel engine parts – rejected products of a high-tech manufacturing firm where he worked for years.  These make the all-time best ever kiln posts for salt.  From him I also got – free, for picking it up in LA – my barstock that I use to set the load.  Here’s a shot of early stages of stack building.

Starting the StackYou can’t see the 3/4″ wads under the shelves, but they are there.  And you can see the big wads on top of the kiln posts, waiting for the next pieces of barstock to be laid over the top of them.  You also can’t see the level that I keep at hand.  I check level on the shelves in both directions – at this point, I rarely need to make an adjustment.  All that wadding helps to keep things level…

I wad all pots that go into the kiln, but I don’t wad salt and pepper shakers, beads, tiny cruet lids, and suchlike.  Because my shelves are carefully cleaned after every firing, this works for me.  I’ve considered experimenting with un-wadded pots, but the potential for variation in vapor movement in the kiln makes me feel safer firing with wads.

So!  If you have gotten this far, thank you…  This is pretty dull stuff, Unless you want to fire a salt kiln.  It’s the only way I know to get effects like this….

Flower Panel


Christmas in November- burning the beast….

Today I get to open my kiln.  I fired it Monday – an anxious firing – and now the pyrometer reads about 450 F on the top and 650  F on the bottom.  I opened the damper and the top port so it will have a little more air in, but will still cool slowly.  About 3:00 I will knock loose the restraining bars that hold the door in place and crack open the top of the kiln so heat will flow upwards out of the top.  AT 8:00 PM  I will open the door and see what I’ve got.  For potters, opening a kiln like this is better than Christmas.  It doesn’t matter that I don’t want to keep the stuff  – it’s an exoneration of the whole irrational process and the completion of two months of work.

I don’t make a lot of work compared to some functional potters, and fire my 24 cubic foot kiln only 6 times a year.  There’s a huge amount of work invested in each load – many small pieces – and there are firing variables that  make each load distinctive.  There are pots that have color or flash that I simply can never duplicate.  If I fired the kiln once a week I might be better able to produce specific effect.   I do keep careful records, and try to use them to make adjustments and conserve fuel.

I said it was an anxious firing – that’s because I forgot to order propane and wasn’t sure that I would have enough.  No space here to go into the physics of propane firing, but when vapor is being drawn into the burners too rapidly it can supercool the whole liquid puddle of propane in the tank and cause “freeze up.”  I’ve experienced this once, and it’s terrible.  Your kiln is almost at temperature and it stalls, nothing works….  that time, the tank was covered with more than an inch of dense, hoary frost.  I had to get a delivery the next day, and start over- gas and time squandered……

The first shelf goes in carefully.  The hardbricks beneath must be cleaned and fresh wadding applied so the shelves can be leveled.  Space between the pots lets the flame and vapor bless every pot equally, nothing nastier than a dry side on a good pot.

Even the kiln posts must be wadded to make precise leveling possible. After many recipes for kiln wadding, I have settled on 1 part alumina hydrate and 1 part Helmar kaolin by volume.  I make a batch during each firing so I will have nice, plastic wads to use a few months later.  It gets better to handle each week that it ages.  I have added wheat flour – nice for workability but it must be frozen if there is excess because it spoils.  I have also added sawdust, which has good properties of you are using larger wads.  Because I make really small wads, I prefer to just use the Helmar-Alum.Hydrate wadding.  It takes 2 hours to shape all the wadding for a firing….  many friends have helped with this over the years.  FYI, Helmar kaolin is a high-alumina kaolin mined in Idaho.  Great stuff for salt-firers, I also use it in my flashing slip, Helmar and EPK, equal parts by volume, skim milk thin.  My wads pop off clean with almost no sanding  – one less thing to do before pricing and packing the pots.

Tallest pieces go into the top of the kiln. I have some solid silicon carbide soaps that make a stable base for high shelves. Every load is different – I was a little concerned about having a shelf up this high but this firing would prove to have good top-bottom heat distribution in spite of it.

I have great Buzzer burners and Buzzer nozzles at this point in my salt-firing career.  No safety equipment for us purists – I just live in the kiln shed for 16 hours.  I love the quiet early part of the firing, calm blue flame…..  I am usually cleaning my tools, my studio, having a rare cup of coffee.  Later, when the kiln roars, its’ power can be frightening.  Once, during a terrible storm, I had 24″ flames shooting out of the burner ports during wind gusts.  I blew up the first kiln I ever built – the memory of that explosion lives in every cell of my body.

But how else can make my pots?