Johnny Chesser

Is plaster of Paris mixed with sand a good liner for a forge?

Recommended Posts

Hello, and welcome to IFI. If you have not already, please READ THIS FIRST!!!

The short answer to your question is, "Yes, and more." It's a bad idea, don't do it, and if you want more information, read the post I just linked and do what it says there.

Share this post


Link to post
Share on other sites

Welcome aboard Johnny, glad to have you. POP and most anything is not a refractory. At best it will erode quickly at worst it can spall and throw bits of HOT plaster around the shop.

Iforge has a LARGE gas forge section with all a person needs to know. Forges 101 is the most current active thread and has info about forges, liners and safety. We're REALLY BIG on safety here. :)

Frosty The Lucky.

Share this post


Link to post
Share on other sites

You made Damascus blades from mild steel?  The point is mild steel has a higher forge welding temperature than high carbon steel.

Regardless, if you are able to forge weld high carbon steel with it you are getting pretty darn hot.  However, the fact that the plaster of paris DIY "refractory" is a heat sink compared to commercial refractory and ceramic fiber blanket still remains.  If/when you change your lining or build a new forge with more appropriate materials you will most likely notice a difference in fuel consumption.

Is that 1400 degrees C or F? 

If you like how everything is working then more power to you, but it's almost a certainty that you are burning significantly more fuel than you would be with the recommended materials.  If you do a fair amount of forging then the cost of the extra propane will probably exceed the savings of using plaster of paris in a short period of time even if it holds up well and doesn't fail in a way that injures you or anyone else.

Share this post


Link to post
Share on other sites

Plaster of Paris is reasonably insulating, but a poor bonding agent, mechanically speaking. The sand makes a reasonably tough grog, but is very poor insulation; result? A poor choice of "refractory."

Share this post


Link to post
Share on other sites
22 hours ago, Johnny Chesser said:

I’ve ran about 250-300 lbs of L.P through it

At our current price of propane, that's about $160.00 U.S. 300lb= 71 Gal @ 2.25 a gallon. Where are you located and how long did it take to use that much propane?

https://www.iforgeiron.com/topic/48833-read-this-first/

 

Share this post


Link to post
Share on other sites

Not to mention that Plaster of Paris starts to degrade around 450 deg F and we will be wanting to use it at over 1000 degrees higher temps!

Share this post


Link to post
Share on other sites

I've used the plaster of Paris and playsand mix in my 20lb propane forge. After about a month of use and not heavy use at all, the plaster degraded enough that I could not use the forge anymore. I tipped the forge up and it all fell out. 

 

Share this post


Link to post
Share on other sites

Ugh, just saw KORs pop/sand mix mini foundry come up on an instructables email. It just won't die. 

Share this post


Link to post
Share on other sites

Bad information keeps getting forwarded by people who do not know enough to know it's bad information.  It's the internet!

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.