Why Whiting Works

[Pamela Theis]

I asked Richard Burkett to explain to me a technical explanation for why/how
whiting functions when added to the salt/soda mixture. This was his response:

Whiting when heated high enough (I can get the exact temp) turns into
calcium oxide (losing CO2) which is really quite refractory (again I
can get the melting point later) IF there's no handy silica or other
material around with which it will form a eutectic. Sodium doesn't do
it, so the sodium (soda ash, soda bicarb) evaporates forming the glaze
while the calcium oxide just sits there waiting to be swept out of the
kiln later. Calcium oxide is not that stable around moisture, so it
will gradually absorb water from the air.

I found this interesting and thought I would share it with everyone.
Pamela

[bryce brisco]

i'm firing a cone 10 salt/soda kiln tomm.... i'm going to give a try...have you tried mixing sifted wood ash into the salt/soda/woodchip mix? i have experimented with is a couple of times and got good results...any thoughts?

[Pamela Theis]

I haven't mixed in with the whiting mix before, but I have blown wood ash into the kiln. I put sifted dry ash on an angle iron and blew with a pneumatic gun and compressed air. I did this around cone 8 and put in about 3 lbs of ash, then I would do wet soda ash (3 -3.25 lbs)in a bucket of water and the same pneumatic gun. Worked great. All the stuff on my website was done that way. Let us know how it works if you mix it in and good luck with the firing.
Pamela

[Emily Murphy]

I haven't put wood ash into the mix but I have sprinkled it directly on the pots in a soda kiln with great success.

[Keith Phillips]

Thanks for posting this... I used Emily's recipe from her blog for the last two firings and like it way better than spraying, or dumping soda straight into the firebox. Spraying seemed to "get soda everywhere", where as the whiting/soda mixture follows the flame path through kiln creating more variation in soda build up which I prefer. Plus the puddle in the firebox isn't there.

[bryce brisco]

i tried the same and seemed to have good results. should have some new photos up by weeks end.
also...going back a bit ( and hopefully not straying from the topic too far)
if the flashing from shells is a result of the salt and not the cal carb, then by that token could you get better shell flashing by soaking them a highly saturated saltwater solution for a few days?

[Michael Kline]

That does sound logical, unfortunately I'm not firing for another month. But I would be cautious about too rich a solution.

[Emily Murphy]

It would be interesting to do a little test. Take 2 shells from the same the source. Soak 1 in salt water, leave the other one with the naturally occurring salt and use them to 'wad' the same piece and see if there is a difference. I wonder if there is a saturation point that is already met from the ocean water... if it would make any difference to do the extra soak. I'm curious!

[Pamela Theis]

I thought that Emily's recipe was posted somewhere here on Ning, but I couldn't easily find it. So, I did some searching on Emily's website and this is what I found. Is this what everyone is trying? Emily is this correct?

1.75 lbs. of soda ash
2.25 lbs. of soda bicarb
4 lbs. of whiting
Mixed together with 1/4 of a 5 gallon bucket of wood chips. Mix together well, then add enough water (while mixing) to the consistency of oatmeal cookie dough. I add it on an piece of angle iron through the ports on the front of the kiln when c. 9 is soft.
*mix the dry stuff with the wood chips, and then add COLD water. Just enough so it sticks together. It should have a consistancy similar to oatmeal cookie dough or tunafish salad.

-Add soda into kiln when ∆9 is soft. Add 1 ½ angle irons full of soda mixture through each port. Wait 15 minutes between additions. Usually takes 3 turns to add in all of the soda.

Pamela

[Emily Murphy]

Thanks Pamela! The direct link to this post is: http://potteryblog.com/2007/11/happy-soda-firing.html

That is my mix (I fire to c.10). Thanks for posting it. A couple of thoughts to add:

*Basically, the proportions is equal amount (by weight) of soda to whiting. So you can vary the recipe for the size of your kiln and the amount of residual soda you already have. Or what type of "soda" you use.

*My source for wood chips varies. I get bags of it from different wood workers. They can vary from almost sawdust to larger (thin) curls of wood. In an emergency (or if you don't have a wood source) you can use wood chips from a pet store.

*It is important to use cold water. If you add hot water it'll turn into a hard plaster before you have a chance to mix it all up.

*Mix it up with water at the last minute. It'll solidify if you try to mix it up early.

*Clean up your bucket as soon as your finished or it'll be nearly impossible to clean it later!

*I use a pyrometer and mark down the temp before I put the 1st round of soda in. The temp will drop when you put the soda in. Then I wait to put the next load in until the temp has risen a bit above where I started. Then I put in the next load and repeat until it's gone. This pacing stops the kiln from stalling out. The temp will drop, but not as much as it does when you spray!

----
The stacking space in the kiln is 3 feet deep, 2 feet wide and 4.5 feet tall. The inside of the kiln is glazed (more on that later!)
The amount of soda used from the beginning of this kiln until recently was:
2.25 lbs. soda ash
3 lbs. soda bicarb
5.25 lbs. whiting
plus wood chips & water.

I recently reduced the amount by about 25% because of the residual soda.

If anyone has pictures of their kiln and pieces from using this message, I would love it if you sent them to me. I will be doing another blog post about my soda process and I'd love to share other people's results.
My email address is: [e-mail]
*Send pictures that are at least 600 dpi
*Any kiln info
*what your soda amount/recipe is
*a link to your website
*any other info that might be useful

It's not something that I am going to start working on for at least another week - so there isn't a super big hurry. Or if you do something in the future, pass it on to me. I always have posts/articles in progress.

This has been a great discussion! I can't wait to read more!
-Emily

[Michael Kline]

Thanks a lot Emily. I'm excited to try your method in my next wood firing.

[Keith Phillips]

As I went to mix up a batch of Emily's mix today, the bucket had some old wadding in there and I went to go clean it out. As I did, I thought of this thread and the thought hit me. If whiting works because it refractory and allows the soda to evaporate, would alumina hydrate work (better?) for the same reason?

Also, just a idea to other, I wrapped the mix in newspaper burritos. Last time the mix kept sticking to the angle iron, also, my soda ports were set for spraying, so I sorta have to maneuver the angle iron over to behind the bag wall. The burritos helps keep it all together while I'm dropping my loads.

[Emily Murphy]

I have found that the key to the mix not sticking is to dump it quickly! But if your kiln isn't set up for that, it would be pretty hard. How did the burritos work for you?