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So I have de-formed the block.  Its not very dry, my workshop is about 15 C and two days in the form didnt do much as the water has no escape. Hovever. It didnt stick on he planks, the block stands solid, now I need for it to dry, then take it home, set it next to heating and then next to owen. I would say....till the end of the week or something. 

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When I did mine it was middle of winter here so it took longer to dry. I did multiple of mine in one go and the way I timed the drying was I got hit with the flu right as I cast them. Once they sat at room temp above freezing for a week I then put them in our powder coating oven to walk the temp up to 500 and melt the crayons.

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15 minutes ago, Sean Blum said:

When I did mine it was middle of winter here so it took longer to dry. I did multiple of mine in one go and the way I timed the drying was I got hit with the flu right as I cast them. Once they sat at room temp above freezing for a week I then put them in our powder coating oven to walk the temp up to 500 and melt the crayons.

It looks like its gonna take a while.  I couldnt get the crayons everybody uses, hence the straws.  I also pushed the manifold quite deep into the brick, but there is still some space inside, altough not much.  Thats my only worry.  Also there is a "mixer" inside and I m gonna put a piece of mesh somewhere into the 2" tube also.  

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4 hours ago, Jaro Petrina said:

...  Also there is a "mixer" inside and I m gonna put a piece of mesh somewhere into the 2" tube also.  

 

A trick some potters use to help mix forced air burners is to place teased out SS wool - the super coarse, scrubby pad kind- in the mixing pipe down stream of the fuel input. Just enough to stick in the pipe and introduce turbulence for mixing, not enough to degrade your turn up. Has anyone tried this on a forced air burner for a forge?

 

Do folks have good results using a release for the straws/crayons rather than resorting to burning or drilling out? What's your plan with the straws, Jaro? I'm going to make a 3x3x6 burner myself, so I'm interested to see how your project turns out.

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The straws should be able to pull out once its dried since the castable does not bond to plastic I believe dowels are similar. Crayons are just soft and short so its nearly impossible to pull them out so its easier to melt out. It depends on your materials and prep you did as wood dowels with nicks and groves will bind but a smooth one should be able to pull out. You want the cast to be dry so it has some stability and hardness so it doesn't break apart.

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14 hours ago, Taylor Hendrix said:

Has anyone tried this on a forced air burner for a forge?

 

It used to be a common recommendation around 25 years ago, but apparently doesn't make enough difference to do anymore.  Might be better in a short plenum ribbon burner, though.

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  • 1 month later...

So I cast the whole thing again, like 14 days ago, but when I unformed today, it was all perfectly wet underneath the plastic plates I used for the form. Also it kind of stuck on sides, so WD40 as a separator sucks. I didnt used straws or anything, I will drill the block once dry. This is taking too much time now. 

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Jaro. Take it slow. That's a big chunk of material that requires a considerable time to Cure. You have a lot of moisture trapped inside that block. Force the curing time and it will crack. Its been a while since I made mine. I used a heat lamp on mine while it was in the forms for a couple days. Rotating it so it go even heat. Once the exterior was hard enough to drill out my crayons I used a hair dryer to force hot air though holes. That helped draw some of the  internal moisture out. Then I used the oven to cook it on low heat (150/175 degrees f.) for several hours.. Then I ran the block on my propane system in cycles. Tedious system but mines still doing fine 3 years later. The trapped moisture inside that block is your enemy. 

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15 hours ago, vlegski said:

Jaro. Take it slow. That's a big chunk of material that requires a considerable time to Cure. You have a lot of moisture trapped inside that block. Force the curing time and it will crack. Its been a while since I made mine. I used a heat lamp on mine while it was in the forms for a couple days. Rotating it so it go even heat. Once the exterior was hard enough to drill out my crayons I used a hair dryer to force hot air though holes. That helped draw some of the  internal moisture out. Then I used the oven to cook it on low heat (150/175 degrees f.) for several hours.. Then I ran the block on my propane system in cycles. Tedious system but mines still doing fine 3 years later. The trapped moisture inside that block is your enemy. 

 

I will wait for a bit, its just lying in the workshop,now,  its temperate but rather wet place.   Many thanks!

 

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