In need of suggestions for my propane furnace

Hey, I am a new member on this forum. I have been metal casting for a couple years now. My first foundry was powered by charcoal and a hair dryer made out of an empty propane tank lined with concrete. It sounds awful, but it was the best I could do as a high schooler with no job HaHa. It did manage to melt aluminum and brass.

As a major upgrade, I just purchased the Devil Forge FB1SB:

Its a 5-10kg propane furnace with a layer of Ceramic wool. Its small, but works for me because I mostly do small projects.
From reading, I understand that Ceramic Wool can be hazardous if not properly sealed. I also read that it can gradually melt or sink in over time.

The Furnace came with a 200 gram bag of rigidizer powder for applying to the Ceramic wool. Im not sure if this will adequately cover the surface area on its own.

My question is: would you recommend buying castable refractory cement to coat the wool? (I know it adds structure and insulation, whereas Im not sure about rigidizer. Or would you use a combination of both cement and rigidizer?

I know they make 3,000 celsius castable refractory which would be adequate for melting copper (my highest goal).

Please advise me on how to coat it, what to coat it with, or anything. much thanks!

 

Here we go........................................................................................................................................................................................................

I'm out.

 

Welcome,
What you need is Satanite.
You paint a layer on, fire the burner to cure it. Repeat the process a couple more times.
The Satanite will create a hot face that increases the efficiency of the furnace.
Only two layers on the lid.

http://www.hightemptools.com/refractorycoatings.html
Five pounds should be enough to coat the furnace but it's cheap so ten pounds wouldn't hurt to have around.

Here's my video on application.

 

Welcome. Good on you for making the effort. Everyone I've heard from who has used satanite for this purpose has been pleased. I also started with charcoal and I still use it from time to time but have moved to waste oil. I also have a crude propane burner that I use for preheat. I've only used commercial refractories so far and the few applications I've had for ceramic wool have completely encased the wool.
The concrete in your original furnace probably held out as long as it did because of the way charcoal burns, but it would fail in short order with a propane burner, possibly explosively, so it's downright dangerous because of the water content of the concrete.
You should be able to melt copper alloys with your new rig.

Pete

 

Don't mind Jason, he's our resident short fuse when it comes to things like Devil forge. Just mention 'king of random' and you'll get on great

All good advice on the coating

 

http://www.hightemptools.com/faq.html#Satanite


Good info here, consider ITC 100, then tell us about your results

V/r HT1

 

Rigidizer will form a hard high temperature coating on the wool. It's like applying varnish except it won't burn, small tool strikes will damage it.

Satanite is very good. One good property is before it's fired it is water soluble, so you can mix some up, paint it on, and let the excess dry in the can. Then add water to the can and it will melt into the water and ready to be used again. You don't have to throw the extra away. The material that gets fired is very hard so it will protect your wool better from damage but I would put rigidizer on first.

Be safe and you'll have fun!

 

After building two furnaces with the Satanite, there are a few things I do differently from the web site FAQ.
I don't spritz the wool first. I mix the first coating a little thinner so the wool will pull the Satanite in deeper.
I haven't found the need to air dry before firing.
Each layer does need to be fired longer than they say. The coating will turn black and then goes to a dark gray, that's a preliminary firing.
A second coat can be applied and then you bring the the whole furnace to cherry red. Any coats after that need to follow that procedure to prevent large shrink cracks.

 

I mostly cast brass 20 sided dice in clay moulds, and various things in lost foam with petrabond sand. I've been experimenting with sand casting with a two part flask, and I would like to do small scale lost wax projects. I plan on casting small quantities of brass, aluminum, copper, and pewter
I have a 3kg clay-graphite crucible. I plan on fashioning a pair of lifting and pouring tongs out of steel bar. My safety gear is pretty solid. I have a respirator, face shield, welding gloves, leather boots, and protective clothing. I do my melting outside, and limit my exposure for the most part. I might need to invest in an apron or make one.

 

Thank you all for the great advice. I really appreciate it
Definately looks like satanite is the way to go. Since the satanite is meant to be absorbed by the wool, would it be bad to first coat with the rigidizer? Would the rigidizeer prevent the satanize from fully penetrating the wool?

 

I checked out the ITC 100 cement. Looks like a good option as well. I'll consider it

 

You'll find a difference of opinion. I think you'll find either route works. After the first layer of Satanite the subsequent layers have to stick to it. I found it sticks to rigidizer, wool, and brick.

 

I HAD to call these sob's out on this one.... Believe me, I'm the last guy on earth to be a safety nazi. I pour over CONCRETE! BOOM!