jrgpots Posted January 9, 2017 Report Share Posted January 9, 2017 The sidewalls of my kiln project are built. The outside of the wall is 4" of hard brick and the inner liner is 4.5" of k26 IFB. The chamber is 30.5" wide x 25" deep x 24" high. I had planned on making the arch as a monolith from a castable. But I worry that the castable will shrink too much during firing and collapse. So here are my questions.... 1. What is the percent shrinkage? 2. Would it be better to cast the arch in sections, like large bricks, fire the sections in another kiln, then assemble thems? 3. Or anybody know where I can get a good price on #1 arch bricks? Jed Link to comment Share on other sites More sharing options...
neilestrick Posted January 9, 2017 Report Share Posted January 9, 2017 Castable is really expensive to do anything large with it. I would think it would be cheaper to buy bricks. You'll still need something on top of the castable to provide additional insulation. I don't think it would shrink so much that it would be a problem. You should be able to find the shrinkage rate of the castable you plan to use in the technical specs. Castable is a great way to do the key brick in a brick arch if you don't want to cut the key bricks. I've done that a few times, and the shrinkage is not a problem. The arch can be built with straight bricks as long as you use mortar (fireclay and sand). Link to comment Share on other sites More sharing options...
Mark C. Posted January 9, 2017 Report Share Posted January 9, 2017 I sent you PM on making your own arch bricks from k26- you can pick up the cheap china made ones online . or buy the good ones below My favorite supplier is Hi-temp-they are on ebay and sell them by the case-they have a great fedex trucking deal so freight is reasonable Link to comment Share on other sites More sharing options...
Marcia Selsor Posted January 9, 2017 Report Share Posted January 9, 2017 I made a castable arch in college for a soda kiln. It was cast in place and did not shrink noticeably. I have also made catenary arch kilns from home made castables in brick bases. They were fine. Marcia Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 9, 2017 Report Share Posted January 9, 2017 If you are using a commercial grade castable, they specify it so you can get that #. In all cases commercial ones shrink very little from the mold size. A home-made castable... it all depends on how you make it (ingredients proportions). Test a sample. Casting full arches is tricky. There are some tried and true aspects that you need to follow. If you have never done it....... try to get with someone who has and learn how to fabricate it well. Fired in place large casts are NEVER fully fired thru. The hot face is fired. The cold face isn't. This sets up micro stress fractures parallel to the hot face. This results in early spalling when compared to previously fired products. The best way to use castable is to cast it, fire it to maturity ion another kiln, and then place it. With large casts... obviously not a possibility for most folks. best, ......................john Link to comment Share on other sites More sharing options...
Mark C. Posted January 10, 2017 Report Share Posted January 10, 2017 Another option is that flat roof I described awhile back from compressed folded fiber held together with stainless threaded rods. My salt kiln roof has this. The roof is about 10 inches thick and it can be flipped if needed later. You could look this post up in the search function on my salt kiln.I have meant to write a piece own this but life got in the way.I have another deal I'm writing about now so this is on the back burner. That roof is easy to make and costs are low.You fold the fiber-in a U-shape. Buy the highest temp you can find for this-which is 2,600 from that hi-temp place I mentions on e-bay. You make a jig from plywood to make this roof.-look up that old post. You have to order and cut and tread the 5/8 to 3/4 inch rods which means metal fab work but it no big deal if you are handy. Link to comment Share on other sites More sharing options...
neilestrick Posted January 11, 2017 Report Share Posted January 11, 2017 You have to order and cut and tread the 5/8 to 3/4 inch rods which means metal fab work but it no big deal if you are handy. Just buy 3/4" all-thread and cut it with a hack saw. The down side of this type of roof is working with fiber. It's not the safest stuff to work with, and every time the door of the kiln brushes up against it you'll release fibers that can be inhaled. Link to comment Share on other sites More sharing options...
Mark C. Posted January 11, 2017 Report Share Posted January 11, 2017 I used stainless rod and we sprayed the roof with ITC but a light coat of rigidizer will stick the fibers so they are not free for and do the same thing for cheap. I'm a brick man myself and we sod not fire the salt kiln very often. Link to comment Share on other sites More sharing options...
Min Posted January 12, 2017 Report Share Posted January 12, 2017 Kiln construction oopsies, Long story short, custom built kiln for us, fellow building them had bought out the company from someone else. New fellow decided to change a few things, he used steel redi-rod and 1/8 rod (not stainless) through the bricks as structural support. (this info was not given to us prior to buying the kiln) Bricks started cracking and being pushed inwards, we began taking it apart to see what was going on, every brick fell apart in pieces as we dismantled it. Found the redi-rod in the door bricks,1/8 rod in the sides and back (front loader kiln). He hadn’t used the rods in the floor so that was okay, we replaced every brick in sides, back and door. The redi-rod where not corroded is 9mm, expanded and cracked bits are about 15 mm. By the time we found the problem the fellow went out of business, go figure. Still irritates me. (slight understatement) Link to comment Share on other sites More sharing options...
jrgpots Posted January 12, 2017 Author Report Share Posted January 12, 2017 Kiln construction oopsies, By the time we found the problem the fellow went out of business, go figure. Still irritates me. (slight understatement) Ouch! Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted January 12, 2017 Report Share Posted January 12, 2017 I have been working my way through this, good read about refractory stuff, broader than the pottery kiln world. http://www.somitmurni.com/Handbook.pdf Link to comment Share on other sites More sharing options...
Mark C. Posted January 15, 2017 Report Share Posted January 15, 2017 heres a link to hi-temp -look at other items for sale as well. They sell all types of soft brick-just send a message asking about items they do not show. This is not a retail store. http://www.ebay.com/itm/141842529038?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT Link to comment Share on other sites More sharing options...
Mug Posted January 25, 2017 Report Share Posted January 25, 2017 Wouldn't a brick arch be cheaper and more durable than the castable ? Link to comment Share on other sites More sharing options...
neilestrick Posted January 26, 2017 Report Share Posted January 26, 2017 Wouldn't a brick arch be cheaper and more durable than the castable ? Yes. Stronger, lighter and more durable, likely cheaper than commercially purchased castable. All the joints in bricks allow for movement and stress release. Arches seem complicated to folks who have never built one, though, when in fact they are wonderfully simple and incredibly strong. That's how we ended up with the Minnesota Flat Top. But I don't see a lot of flat roofs that are still around from Roman times. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 27, 2017 Report Share Posted January 27, 2017 The Minnesota Flat Top roof is actually harder to do "right" than to build an arch of the same span and support it well. best, ..............john Link to comment Share on other sites More sharing options...
neilestrick Posted January 27, 2017 Report Share Posted January 27, 2017 The Minnesota Flat Top roof is actually harder to do "right" than to build an arch of the same span and support it well. best, ..............john EXACTLY! I've always thought it seemed like way more work than an arch! Link to comment Share on other sites More sharing options...
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