Insulating a propane forge

[Jerwald]

Hello everyone 

I'm a new member on this site and looking to get into knife making on a small scale, just as a hobby. 

I'm trying to build a small gas forge for heat treating so I've been browsing and researching a fair bit. Attached is a picture of a shell of a forge that I'd like to make. It's out of galvanized ducting which I've read might not be a good idea. Any thoughts on that?

Also I'm not quite sure what to do about the lining. I was intending to go the plaster-of-paris/sand way but I've read a fair number of comments saying "don't" so I'm looking for advice. Im trying to build a portable forge as I don't have an area where I can set up something permanent.

Thanks in advance, looking forward to responses

Jerwald

 

[Irondragon Forge ClayWorks]

Welcome from the Ozark mountains.

As far as galvanized (think metal fume fever) in a forge it is not a good idea unless you remove the coating. I suggest reading some in this section.

https://www.iforgeiron.com/forum/159-zinc-galvanized-and-coatings/

This section should answer any questions you have about lining the forge, just need to some reading here. Plaster of Paris and sand is not only a bad idea it can be dangerous.

This thread will help with a lot of questions.

https://www.iforgeiron.com/topic/61288-my-consolidated-notes-for-new-forge-builders/

 

[Frosty]

Welcome aboard Jerwald, glad to have you., If you'll put your general location in the header you might be surprised how many members live within visiting distance. Person to person time with experienced smith will teach you more in a couple hours than days or weeks trying to figure it out yourself.

Galvanized is NOT a good idea, zinc oxide fumes can be VERY toxic. Heavy wall, black stove pipe is safe and can be worked with hand tools, SS stove pipe is as safe if kind of expensive.

There are a number of proven pipe forge designs in the Forges 101 section. The internal volume and shape will determine the size, number and placement of burners necessary to heat your forge. 

Frosty The Lucky.

[ThomasPowers]

Basically I would disregard *ANYTHING* from a site that advocates using Plaster of Paris and Sand as a refractory; sort of like: would you use medical advice from someone who advises dipping your medical tools in human manure before use?

As for shell material; I have used grain tube from silos or welding tank material.  (NOT ACETYLENE TANKS---no way to make them safe to cut and use! O2 Ar, Co2, N2, etc.) The grain tubing was nice and light but degraded, didn't last over a dozen years.  The gas welding cylinder is still going strong at over 20 years and multiple relinings!    If you will be moving your forge a lot you may want to make the shell fairly rigid to keep the lining from flexing.  Some folks use BBQ propane bottles or even Helium party balloon tanks---always a supply at my scrapyard though the price has gone up to 25 USCents a pound now...