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Old 01-10-2018, 03:23 AM
epicfail48 epicfail48 is offline
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Rutlands 'Furnace' Cement, A Warning

Its not too often that i make a post solely to badmouth a product, but this one really needed to be said. As a few members here know, ive been spending a while trying to get my kiln working at higher temperatures, but having some problems with element life. Mainly, i kept melting elements. At first i chalked it up to simply running the elements on too high of a power draw, and ended up building an entirely new enclosure to fit the extra needed wire to get the element surface load to well below the recommended levels, which shouldve led to everything working perfectly.

In a twist that should surprise absolutely nobody, the elements melted again. I double checked my math of course, and with the element arrangement i had, i was well below the recommended surface load at 16w/in^2, so power clearly wasnt the problem here. Also not the problem was excess temperature for the wire, age of the elemenets, or any of the usual suspects.

Instead the problem, as i found out after removing the elements, was the mortar used. I had used the Rutlands black furnace cement, sold at Home Depot, comes in a standard caulk tube and claims to be good up to 2000f, a claim it does not live up to. At about 1700f, as it turns out, it liquefies and oozes out of the joints:


Thats what it looked like on the element that DIDNT fail, and sure enough on removing that element there was a gob of what looked like glass stuck to it. The element that did fail looked like this:


The mortar ate through the element acd caused an arc fault, which proceeded to liquify the firebrick itself and leave a 1/2" void in the wall of my kiln. In addition to that, half the mortar joints themselves failed, leaving the floor of my kiln separate from the walls. Im rather glad i discovered that when the kiln was cool.

Again, this was all well below the recommended maximum temperature of the mortar, but thanks to it i now have to spend the money to replace 2 elements and buy a different mortar, as well as waste the time sawing apart each joint in the firebrick to get out the faulty mortar. As you can imagine, im pretty bloody pissed about that. Anybody whos building a kiln of their own, learn from my mistakes, and stay the hell away from Rutlands. Ill be ordering some Sairbond, once i actually have money. Hopefully theyll be more worth the price.
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Old 01-13-2018, 07:59 AM
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Crex Crex is offline
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Might I recommend getting your mortar from a reputable furnace service/repair Vendor/Store. Home Depot is just not the place to get quality materials for projects such as your HT oven. I too, have had to learn that and understand your dissatisfaction. I don't even like to get plumbing supplies from them anymore.....three trips to get the right fitting because of what the label and the store expert says, then you still have to make modifications for it to work.......I'm getting good at finding better sources these days.

Hope the change up works out much better for you.


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Old 01-13-2018, 12:54 PM
epicfail48 epicfail48 is offline
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Quote:
Originally Posted by Crex View Post
Might I recommend getting your mortar from a reputable furnace service/repair Vendor/Store. Home Depot is just not the place to get quality materials for projects such as your HT oven. I too, have had to learn that and understand your dissatisfaction. I don't even like to get plumbing supplies from them anymore.....three trips to get the right fitting because of what the label and the store expert says, then you still have to make modifications for it to work.......I'm getting good at finding better sources these days.

Hope the change up works out much better for you.
Yeah, it was my mistake thinking it would be a good idea. In my defense though, the thought process was something along the lines of "eh, if something goes wrong the worst i have to look forward to is a joint failing". The idea that the cement would melt, expand and fry my elements didnt even register
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Old 01-14-2018, 06:27 AM
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Crex Crex is offline
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Me too, but only once. Second forge build everything cooking along just fine then the inside top and sides just turned to glass and slumped to the floor of the forge making a real mess. The stuff I got came in a tub and said rated for 2700 F on the back. I was running the forge about 1750 F. Sometimes we get bit by the "friendly" dog.


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