Sand or vermiculite

[gmack]

Just setting up my new hobby cdl evaporator and wondering if I should use sand or vermiculite for the back of the arch .

Thank you

[BreezyHill]

Vermiculite or even speedy dry will insulate better than sand. I used speedy dry last year and it worked great. Vermiculite we had on the farm, but felt it would move easier and settle more.

[Thompson's Tree Farm]

sand will also hold more moisture which can damage the arch and is much heavier than vermiculite.

[maple flats]

An arch is not strong enough to hold sand if it gets compromised. Use the vermiculite and then cover it with a layer of brick or even just a thin layer of refractory. You can use dry refractory and the use a mist bottle to lightly dampen it several times. Then heat slowly as prescribed in the directions and it will harden to protect the vermiculite. For the vermiculite, go to a commercial greenhouse supplier such as Milikowski, or Griffin or similar. The vermiculite will cost a small fraction compared to buying small bags from a big box store like Lowes or Home Depot. You can use large or small curd.

[PerryFamily]

Vermiculite
I got a large ( contractor bag size) bag from our local vegetable farm coarse grade for $32.

I covered mine with blanket . will just have to be careful if you clean the flues.

[morningstarfarm]

What we have always done is use vermiculite then cover with about a half inch of dry mortar...then lightly spray the mortar with water...it hardens nicely and holds the vermiculite in place...good luck

[PACMAN]

I used play sand in my 2 by 8 and its been good for 3 years.

[maple flats]

I suppose I should clarify my statement some. If you have a drop flue it might be OK, but if a raised flue you are adding far too much weight. In fact, play sand, bought in bags may even cost more than if you bought vermiculite from a greenhouse supply, if you buy from a big box store, then the sand would cost less. When I bought mine about 7-8 yrs ago, if memory serves me,I paid $17-19 per bag for 6 CF bags. I don't know how much the price has climbed since then.

[Swampmapleman]

I wouldnt use sand because it will probably hold too much heat. When it comes time to shut down you might be hanging around awhile.

matt

[brookledge]

Avoid sand. It holds moisture. I guess if your whole arch is stainless then it would be ok but vermiculite is so easy to work with. And as already stated a little mortar on top with a spray will harden up just enough so that the vermiculite doesn't move
Keith

[Stoneduster]

I sometimes use a 6:1 vermiculite/portland cement mix to insulate chimneys. I dry mix the ingredients, then mix in just enough water so that when you squeeze a handful of the material it will stay together in a clump, but not so much that excess water gets squeezed out. Once the mixture sets up, it will keep the light, insulating qualities of the vermiculite, but will be fairly stiff and will stay in place.

[BreezyHill]

Avoid sand. It holds moisture. I guess if your whole arch is stainless then it would be ok but vermiculite is so easy to work with. And as already stated a little mortar on top with a spray will harden up just enough so that the vermiculite doesn't move
Keith

Don't forget that vermic holds 10 times its weight of water. It is used in the horticultural industry to hold moisture for plants in pots.