karen terpstra on mon 8 apr 02
Hi folks.
well here's the report of last week's soda flat top kiln building
workshop with Mel. A very good learning experience! As you can tell
from the subject line, we had some trouble and I'll explain what
happened.
The building of the kiln floor, walls, flue, etc. went great. We used
a hard brick interior and soft brick exterior because we will use this
kiln with soda. The soft bricks are about a quarter of an inch bigger
than the hard brick so we did some filling in on two corners of the kiln
and leveled with mortar at two places. Wasn't a big deal.
We had two thirds of the work done before Mel got there. When Mel
arrived, he said, "My god this thing is big!" (about 35 cubic feet
interior space). Turns out Mel and I had our wires crossed when we were
discussing the feasibility of a hard brick flat top kiln! He thought
it was only 25 cubic feet interior space! Mel was cool! Went on to
explain the advantages of this type of design for people who have to
build a kiln themselves. (only don't do one this big with hard brick)
Well, we went ahead and tried it. It was a hands on learning experience
for students. That was the important thing last week. There were lots
of students and guests there who really needed to know how to build an
easy-to-build kiln. And now after doing this, I am convinced that this
is the way to go for a SMALL hard brick kiln, or a soft brick kiln of
any size. I have a couple students who are ready to take flight and
build a small kiln in their garage. This plan is ideal for them. Only
don't do the hard brick flat top as big as what we tried.
When Mel and I saw that we were going to have trouble, we put a thin
castable over the top after we lifted it one and a half inches. We were
hoping this would work. Unfortunately it didn't. Maybe the bricks
dried to fast before we had things tightened up. Maybe it wasn't going
to work anyway.
When we pulled the jack out and the wood form for the top, we lost 8
bricks in 2 rows which means replacing the both rows in this design. We
have another area in the top that is questionable too. We could
probably fix it and try this and that but it is not worth the risk to
students work or mine (or my sanity).
When bricks heat up and during the firing, they expand and you don't
have to worry about bricks falling out. But, during cooling they
contract and that's when they could fall out. I don't want to have to
go through the worry for the rest of my tenure here.
So, now that my students know how to build a flat top and what not to
do, we are going to build a sprung arch on it. Luckily we have enough
brick.
I was anxious to try the new burners we bought from Nils Lou. They look
phenomenal and we even started them up for just a few seconds when the
wooden forms were still in the kiln. I just couldn't wait! Like they
say on TV---don't try this at home!
So, those of you contemplating a flat top kiln, I'm posting this so you
don't make the same mistake I did. For a small hard brick kiln...it's
fine. For any size of soft brick kiln, it's the way to go!
There you have it.
Happy firings!
Karen Terpstra
La Crosse, WI
Brian Molanphy on tue 9 apr 02
hi karen,
thanks for the report. would you tell us, how big (length x width) was the
hard brick flat top that didn't work? what size hard brick flat top would
not collapse, in your estimation?
thanks, brian
'...When we pulled the jack out and the wood form for the top, we lost 8
bricks in 2 rows which means replacing the both rows in this design. We
have another area in the top that is questionable too. We could
probably fix it and try this and that but it is not worth the risk to
students work or mine (or my sanity).
When bricks heat up and during the firing, they expand and you don't
have to worry about bricks falling out. But, during cooling they
contract and that's when they could fall out. I don't want to have to
go through the worry for the rest of my tenure here...'
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