Jump to content
  • Announcements

    • Jennifer Harnetty

      Moderators needed!   12/08/2017

      Ceramic Arts Network is looking for two new forum moderators for the Clay and Glaze Chemistry and Equipment Use and Repair sections of the Ceramic Arts Network Community Forum. We are looking for somebody who is an active participant (i.e. somebody who participates on a daily basis, or near daily) on the forum. Moderators must be willing to monitor the forum on a daily basis to remove spam, make sure members are adhering to the Forum Terms of Use, and make sure posts are in the appropriate categories. In addition to moderating their primary sections, Moderators must work as a team with other moderators to monitor the areas of the forum that do not have dedicated moderators (Educational Approaches and Resources, Aesthetic Approaches and Philosophy, etc.). Moderators must have a solid understanding of the area of the forum they are going to moderate (i.e. the Clay and Glaze Chemistry moderator must be somebody who mixes, tests, and has a decent understanding of materials). Moderators must be diplomatic communicators, be receptive to others’ ideas, and be able to see things from multiple perspectives. This is a volunteer position that comes with an honorary annual ICAN Gold membership. If you are interested, please send an email outlining your experience and qualifications to jharnetty@ceramics.org.
Sign in to follow this  
Jude

Wadding...does it need to dry much before firing?

Recommended Posts

Hi I am new to participating in this forum. Have been using the site and your discussions to educate myself on all aspects of kilns, firing, glazes etc.

Just discovered "wadding" recipe (by John) and uses...wow!...so basic question...how dry does wadding between props and shelves need to be before firing? (low temp ...1080C)

Thanks so much for consideration and responses.

 

kindest thoughts across the waves and oceans in New Zealand

Jude

yappystudent and Biglou13 like this

Share this post


Link to post
Share on other sites

I've  seen where wads are placed one day (relatively fresh) then fired the the next day and in a few cases within a few hours..

most of the wood firings had a slow ramp

but great question!!

Physical water starts leaving at 212F    so if your being careful. Hold around there  or slightly higher, chemical at 1000f ish 

im curious because the wadding reipies ive used are a bit loose with organic material,  sawdust, rice hulls, coarse sand,  and nowhere near compressed , and rarely if ever more than  3/8 inch thick  ... I'm thinking the "looseness" of the wads allows water to escape in a non explosive manner.

i look forward to the leaned minds comments  

Jude likes this

Share this post


Link to post
Share on other sites

I think Biglou13 is correct about the slow ramp and "loose" nature of most wood fire wadding is correct.  I have done a couple minor preheats on propane just to get a little of the moisture out.  My wadding is usually 1/3 fireclay, 1/3 sand, and 1/3 organics (usually sawdust or wheat bran) so there is lots of ways for any moisture to move around.  I do make large cone packs from a version of the wadding with much more clay and I let those dry before firing. 

 

Jude likes this

Share this post


Link to post
Share on other sites

do i remember a potter who made his wadding and flattened it by rolling like a thickish slab before cutting it into equal squares with that ceiling diffusing plastic grid?  yes, i do and he reused some of it.

Edited by oldlady
D.M.Ernst, Rae Reich and Jude like this

Share this post


Link to post
Share on other sites

HI ALL.... I think I've been unclear...electric kiln...wadding mixture as follows from elsewhere on the forum..John I think..

"Kaolinitic Clay" as a term (unusual) basically says it is something that is more or less a kaolin.  Mix that 50% with 50% alumina hydrate... and you have "kiln wadding".  Any kaolin with 50% alumina hydrate will work as wadding pretty darn well.  In fact,...... for gas and electric high fire...... 50% kaolin and 50% silica works OK.  Or 33.3% any kaolin, 33.3% alumina hydrate, 33.3% silica is a pretty standard kiln shelf wash mix that makes a good (non woodfire/salt fire) wadding also. 

6 hours ago, Biglou13 said:

im  curious because the wadding reipies ive used are a bit loose with organic material,  sawdust, rice hulls, coarse sand,  and nowhere near compressed , and rarely if ever more than  3/8 inch thick  ... I'm thinking the "looseness" of the wads allows water to escape in a non manner.

 

Edited by Jude
Biglou13 likes this

Share this post


Link to post
Share on other sites
Guest JBaymore

While there is certainly the possibility of a piece of wadding popping because of steam forming too quickly at 212F (100C) ........ I've never seen it happen.  I mainly use it in wood fire these days, but sometimes I used it in salt and soda fire in gas kilns a long while ago.  And I still occasionally will wad a piece in a gas kiln to this day.  Typically pieces and posts are wadded one day and then firing started as close as the next day.  Sometimes loaded and then fired as much as a week away.

Wadding is typically used in very small pieces.  Often lots of surface area relative to the volume.  The material itself has large particle size, so the migration of water from the interior to the exterior is pretty "open".   When it is contained between post tops and the shelves, even if it cracked due to steam issues, it likely will just stay where it is until unloading......and then you wouldn't notice that it cracked.  A real "bang" not so much though.

Wadding is almost always placed against both a piece and a shelf or a shelf and a post.  These relatively large thermal masses touching the wadding tend to slow down the heating of the wadding itself.  So if the air/gases circulating past the wadding is at or over 212F (100C), or if radiant transfer is happening in that area, there will be a tendency to "retard" the rapid climb on the wadding itself a bit. 

BIG thick jumble stack wadding is usually loaded with a lot of organics.  Sawdust, coffee grounds and the like.  There is more of that stuff than "clay".  It dries out very easily, and is very open to the migration of water.  So this style does not tend to pop even though it is often pretty thick... and applied in inches and inches thickness.

Do remember in wood fire, not only is there the natural by-product of combustion that is water vapor, but even "dry" wood has some more water that is contained in the wood structure.  So in the very early stages of the firing, the warm gases that are circulating in the kiln chamber are very "humid".  The partial pressure of water vapor in those gases is high,.... so that "evens out" and slows down the evaporation rate of water out of any wet materials ion the kiln.  Add to that the fact that a wood kiln typically is being ramped up kinda' slowly for a LOT of reasons (like flame quenching on cold refractories in the firebox.  So the treatment is pretty "gentle".

This sort of resembles how industrial drying units work.

In an electric kiln, with no combustion going on to produce any water vapor, the air in the kiln is quite low humidity (depending on where you live and how humid the climate it).  So there is a tad more "risk" there that it might happen.  I've never used it in an electric kiln.  (But I have frequently made fresh cone packs -with very little clay- and placed them in electric kilns and fired them almost instantly... and never blew them up either.)  So I'd be a tad more careful than us woodfirers are.

Them's my thoughts.  :)

best,

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

 

Share this post


Link to post
Share on other sites

I fired some wadding in my electric kiln a few months ago. I did about 6 pots. I made the wadding up right before the firing and added it to the pots. I just added a 1 hour preheat and fired away. There were no signs of cracks or explosions. Everything came out fine. 

I just mixed Kaolin and Alumina Hydrate together 50/50. Seemed to work fine.

No idea if this is helpful to you or not, but just some experience from my end. 

Jude likes this

Share this post


Link to post
Share on other sites

I have at times in the electric firing, had to raise a piece above the shelf a bit to allow it to fit in with other pieces in the kiln, most times I do this with broken shelf sections. I have often thought of using wadding as when firing salt firings it was quite useful to change height of an object with a little bit more wadding. I may try it out some day.

As for the cone packs, I have blown up a cone pack in a few firings and am now very careful how I make my cone packs, and dryness when loading the kiln. I use a cone pack with alternating fall directions perpendicular to the cone pack length. I also perforate the cone pack with a series of pencil point piercings.  and make the pack early and place it in the sun or in front of the shop heater before loading into the kiln. This helps quite a bit as I have not had an exploding pack in quite a while.

best,

Pres

Jude and Rae Reich like this

Share this post


Link to post
Share on other sites

when I use wadding its always mixed up in a sealed plastic gallon bag. It firm but moldable. never wet, I use it in slat kiln and to retire salt pots in reduction kiln. I use brown shelve pieces in all dimensions to stack the shelves. I have a bunch of small 3/16 advancer pieces and some 1/2 inch and 3/4 inch mullet and carbide pieces . They are all washed and do not stick to posts. I have called them nerds for 4.5 decades and no matter what you call them they are nerds to me.

I never use wadding in my weekly reduction or electric firings-I could but its no need as the stacks are solid .

Share this post


Link to post
Share on other sites

FOLLOW UP:

thanks again everyone!! :-))))

Used the shelf wash mix to make a paste ...I used it to repair jagged edges on my props so I felt more confident when they are stacked....it wasn't applied too thickly...and dried pretty quickly but I still waited a couple of days JIC and it all fired with no problems...great stuff that wadding

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.