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Lars 06-17-2009 10:04 PM

Tamping tool, or home-made curved trowel.
2 Attachment(s)
Here's how I plan to lightly tamp on the vermiculite portland layer and also shape a spherical dome.

I wanted to make a curved makeshift trowel. Just a piece of masonite, tileboard, or sheet metal, of the proper length, tacked on to a 2x4 handle. Since my oven is 39" inside diam,the extra 9" of fire brick gets you to 4 feet diameter for the dome, and add 6" all around and the diameter is 5', so , a 30" radius on the trowel arc.

The first notion involved some angled boards and some biscuits, perhaps, but then I decided to REALLY make it easy ( and MUCH stronger and functional) but just clipping off the ends of a 2x4 at 30 degrees, then attaching them below!
( see the drawing)

On the sides I am using metal lath. After scratch coat, I should be able to fill with the vermiculite/portland out to 6" or so. Then on top, I am going to use blanket under and tamp the vermiculite on with this arched tool ( hopefully) What's cool about a curved trowel is, it really should start to define a sphere much the same as a flat trowel defines a plane.

I'll post the outcome.

Neil2 06-19-2009 05:29 PM

Re: Tamping tool, or home-made curved trowel.
1 Attachment(s)
Or something like this:

Lars 06-19-2009 06:22 PM

Re: Tamping tool, or home-made curved trowel.
Thanks for the pic!

I made up my 'trowel' and used a metal lath for holding in my ( portland rich) vermiculite layer.

From what I can see, you did not use a blanket. Is that correct? If so, how satisfied with your heat retention are you? Does your outer shell get very hot?


Neil2 06-21-2009 10:38 AM

Re: Tamping tool, or home-made curved trowel.
No blanket.

Just 5 inches of vermuclete (a 1:12 mix). Works fine.

Lars 06-21-2009 11:18 AM

Re: Tamping tool, or home-made curved trowel.
I only have 2.5" vermiculite on the base, and it gets more and more insulated as you go up the dome. First 10" about 4" vermiculite layer, above that 1" of ceramic blanket under the vermiculite ( still 4") and then I will be putting at least 2" of ceramic blanket over the whole top half of the dome then covered with 4" vermiculite.

I was in kind a hurry to get started and didn't fully understand the lower.

Today is Father's Day... my second 'curing' fire. Should be fun!


Lars 06-25-2009 01:58 PM

Re: Tamping tool, or home-made curved trowel.
3 Attachment(s)
On my third curing fire, I noticed the bricks in the center of the dome top get rather warm first. It takes quite a while, AND, in the meantime, the dome bricks just 10 inches around the center top are still rather cool.

So, my idea that more insulation on top might increase the efficiency of the oven/insulation make-up might hold true. I decided to put 1" of blanket on MOST of the dome, and put an extra 2" inches of blanket over that on the top 4 sq. ft. or so. I got the blanket from a place that just had it lying around for a 'contribution to the beer fund', but it looks like it will be pretty good.

Pictured you can see my 'curved trowel' described in this thread.

dmun 06-25-2009 02:40 PM

Re: Tamping tool, or home-made curved trowel.
The top of your dome will always get hot first. When you get to full heat, your top will burn "white" before the rest of the dome, and the burn off will creep down toward the floor. While more insulation is always good, don't be alarmed that the top is hotter: heat rises.

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