Soldering hearth

Get some firebricks or ceramic wool.

No connection, but have bought clay, sand and talc from them...

Mark Rand RTFM

Compressed vermiculite blocks are light and very good insulators so they make a good hearth. However they have the mechanical strength of a Nice biscuit so are pretty limited if you move bits around much ? on the other hand they can be sawn to any shape you want just using a hand saw.

I make my hearth up as I need it using a pile of standard firebricks which I got from Travis Perkins (only the bigger depots carry them but mine was quite happy to order them in) ? virtually indestructible but heavy. I have some of the vermiculite blocks which I use on top for particular jobs. The firebricks cost a tiny fraction of the price of the vermiculite ones when I bought them.

Also worth looking at the insulating blanket which CuP alloys sell. It?s spun ceramic fibre and a terrific insulator. You can do small jobs just on a piece of the blanket and it?s also good for wrapping around things to keep heat in.

Word on the blacksmithing groups is that the dust from ceramic fibre can be hazardous - it's usually recommended that it is coated with some sort of binder.

I've made a furnace using castable refractory mixed 1:3 with polystyrene beads. The beads have to be burnt out (which is easy in a furnace, more difficult otherwise. It leaves a highly insulating "honeycomb" material which is reasonably strong. The advantage of this material is you can make it whatever shape you like - even casting bricks if that's what you want. (I've used a couple of bread tins to cast bricks)

You can buy body soluble blanket which is much safer than the normal ceramic fibre blanket. IIRC the common fibre blanket temperature capabilities are 1260C and 1420C, at least the ones I normally use. The body soluble stuff only goes upto 1260C IIRC and is more expensive. Don't know anyone that sells small quantities, only by the roll but I haven't looked.

The ceramic fibres used these days are required to be bio soluble. That doesn't mean that they'll wash away with water, but if in contact with wet soggy bits of meat for a prolonged time, they break down into non-hazardous sized lumps small enough to be dealt with by the macrophages in the lungs.

Mark Rand RTFM

Mark,

Do you know that for a fact. My knowledge of the subject, from my involvement in glass blowing, and speaking to my main refractory supplier, IMS Wright Refractories, is that both are available but the body soluble stuff doesn't have the temperature capability of the stuff you have to be careful with. IIRC the body solubility has to do with MgO in the fibre mix but it reduces the maximum temperature the fibre can work at so for a glass blowing glory hole the safe stuff isn't suitable.

Nah, it was an incomplete subset of the whole thing :-( although I get the impression that that's the way that Brussels wants to go.

The stuff I use is calcium silicate based. They occasionally use the odd few pallet loads at work to wrap bits of turbine rotor that are being head shrunk together or apart. Sometimes, I can blag a couple of square yards of it if there's a part roll left over.

It's only good for 1000C but, with care, can be used for brazing and hardening duty. Goes brittle due to getting it too hot when the torch is played directly on it for too long.

Mark Rand RTFM

You can buy insulating firebricks that are significantly lighter than conventional "heavy" firebrick and also have significantly lower thermal mass - I have a load that I bought a while back for pottery kiln repair & a few of those stacked together makes a good hearth. They can be had from pottery material suppliers.

Regards, Tony

My thanks to Norman and Mark.

Cliff.