Relining Options

[Steelfinger]

Hey Gang,

I've had a Majestic forge (the 2 burner knife maker) for about 4-5 years now. I've never had a problem really, some concern from reading bad things after I bought it, but that couldn't be changed, and she served well.

She has been slightly abused. The top of the mouth warped, which split the soft fire brick there. I've also heard tell they're not as good as others when it comes to insulating.

It's also fun to note, I just did a quick search on the forum, and a recent posting talked about running the forge at maybe 8-12 psi, while I'm usually in the 15-20 range, tuning down to 5-7 to idle her. no wonder I use propane so xxxx fast. I also try to keep the mouths closed with a pile of hard firebricks (from my first forge attempt) but not sure how well that's working

So here's my questions:

-when is it worth while to reline a forge?

-what are the options, and which would make it harder to cook an egg on the top of the thing? I've only seen bricks and some refractory cement (which, no idea where to grab it)

-are firebrick soft and hard worth using again, and where might I find more softies (I think my brick supplier only had hardies, or I used the wrong words)

what the xxxx, While I'm here

-is it worthwhile to run oxy through with the propane, or would this only mean more scale? 

 

This might be too much restriction, and I know I need a good lining to keep the forge going good and save money on propane, but I'm still a starving college student. I was hoping to get some work done on summer break come august, and someone's gotta buy me beer and smokes. I'm not saying cheaper options, but cheaper ways for good options.

oh yeah, I've got some slag built up on the bottom hard fire bricks. tips n tricks? I know I shouldn't be resting anything on the bottom, but xxxx I touch that puddle on accident and come out with a good glob I gotta wipe off and pray against.

[Frosty]

You gotta watch your language, Admin is going to be xxxing this hard and shooting you a warning. Please don't get yourself moderated!

Yeah, you can really improve a Majestic, they have pretty much commercial standard liners. Or in other words not so hot. There are a couple basic options for upgrading the liner: 

#1, lose the fire brick, hard is lousy insulation, only slightly better than an equal thickness of limestone. It's also a strong heat sink meaning it's going to burn a LOT of fuel getting it up to temp and keeping it there. Soft fire brick is decent insulation but has a pretty low tolerance for thermal cycling unless you buy the expensive kind. Borax based welding flux dissolves silicates hard fire brick erodes pretty quickly and soft very quickly.

Better insulation will mean a forge that heats up quickly and doesn't require nearly as much fuel to maintain temperature. The two main insulating refractories are: #1, ceramic blanket, I use the brand name Kaowool in reference to it for my convenience, not because it's superior, there are a number of comparable and some superior brands. The other main type is ceramic fiber board, Fiberfrax being a brand name.

Ceramic blanket is a little better insulator but there are tricks to getting it to stay in a flat roof, rigidizer and a few screws do the trick. refractory boards can be cut with a saw and placed like building blocks which is really nice. Unfortunately ceramic board is considerably more expensive and usually not sold in small quantities. 4' x 8' sheet is  spendy.

In either case welding flux dissolves it like hot water on cotton candy and it's fragile at forge temps. A hard refractory inner liner more properly called a "Flame Face" is the simple solution but it's important to choose the right type. Currently the popular refractory is Kast-O-Lite 30, it's a water setting, high alumina bubble refractory with a working temp of 3,000f. Water setting means you mix and use it like Readycrete concrete, it hydrates to harden not dry. High alumina refractories don't suffer from the caustic nature of molten borax so chemical erosion isn't a factor, it's concrete hard at 3,000f so you don't have to baby it. The bubbles are evacuated silicate spheres which make it lightweight AND an insulating liner. 

Just 1/2" makes the inside of the forge proof against temperature and flux while protecting the insulating outer liner. Laying it a LITTLE thicker on the floor is a good practice but it doesn't need to be THICK, 3/4" is plenty.

A final kiln wash using a zirconia product like Plistex or Metrikote makes the liner MORE chemical resistant but it's real benefit is zirconium is a strong IR re-radiator. It has a very high thermal mass so it takes a lot of time to conduct through it while it holds it like a battery and re-radiates it.

Re-radiating heat is how a "regenerative" forge works, the flame heats the liner which radiates IR and the IR heats the stock. A good kiln wash enhances the effect while preventing the rest of the liner from getting as hot. So yeah the outside of your forge won't get as hot. My latest forge has 2" of Kaowool backer, 1/2" Kastolite flame face and a home brew zirconium wash and after several hours of working you can touch the forge shell it's about as hot as a cup of coffee.

Frosty The Lucky.

 

 

[Steelfinger]

Well, I certainly see the xxxing, no messages yet though.

If he did, I'd reply personally. Since he hasn't I'll anticipate he reads this, and I'd like to apologize. It certainly wasn't directed, which would be worse, but its still an inappropriate shop language I've developed. I'm smart enough to know better.

I took the step to contact Jim Walls who makes the forges. He doesn't recommend the coatings I'd heard about (didn't mention the name, I forgot it. Plistex and Metrikote, credit to Wayne Coe from when I was considering it, might even have to buy it from him, but that was three years ago). Jim also suggests a reline (same material of course) for about $160(!) plus probably duty both ways to cross the border.

My guess is those are somehow incompatible with the soft firebrick? Or maybe a secret deal with the propane companies. Either way, I kind of anticipated that sort of reply. 

I'm not sure what I can grab close to me. I'm trying to find something, I'm sure either Home Depot or a landscape place should be useful. I'll follow up on research.

I'm also curious if anyone viewing has seen carbon foam,such as this Carbon foam Making video, or this Loaf of bread foundry, both of which are swear-filled, but informative. Some might also find his humour off-putting, and I apologize. I hope a warning is enough for these. Any ideas how good this would be, not that mum would be happy if I started burning bread. The foundry video also looks like that stuff wouldn't last long.

[Michael Cochran]

1 hour ago, Steelfinger said:

I'm also curious if anyone viewing has seen carbon foam...

I haven't messed with it but with my limited knowledge I'd imagine it wouldn't last. Seeing as charcoal is mostly carbon and it's burns readily I doubt carbon foam would last well for any period of time. 

[Frosty]

None of the commercial forge makers recommend you do or use ANYTHING but their liner kits.

Did he say what the brick like object on the floor is? If it's good I'm interested, none of my forge and burner opinions are set in stone. Well, those that aren't safety related of course. Don't turn the gas on, go have a cup of coffee THEN toss in a match! (Silly example but . . .)

Carbon foam might make a decent insulating refractory if you use it in a vacuum or inert atmosphere. Even graphite will burn and the carbon carbon tiles on the shuttle are ablative.

If you're more comfortable buying a liner kit from Majestic that is the way you should go. Seriously, it's a quality forge and the lining has lasted you  years. It doesn't sound broken to me, the only reason to try something new is if YOU want to tinker. Lots of us thrive on tinkering and like helping other folk play.

Frosty The Lucky.

[ThomasPowers]

come on now---even *diamonds* will burn if you give them enough inducement!

[Mikey98118]

You are between a brick and a hard shell

Without dissing your forge, it boils down to a question of room. You need a tough hot-face on the one hand, and insulating qualities on the other; your forge just doesn't have the room to give enough insulation and maintain physically tough interior surfaces. So, compromise with a good tough semi-insulating hard refractory like Kast-O-lite 2600. Kayolite brand has a good variety of insulating and semi-insulating hard refractories, too; look them up. Building a shellacked wood form to cast your own brick floor in, is simple. You can buy either brand of refractory in small amounts from re-sellers (like Wayne on this very forum). Go to the Forges 101 thread, and read up about zirconia silicate homemade refractory and kiln wash, which will reflect heat back into the forge. You can buy the supplies at most pottery supply stores. You wont lose or gain any money going this rout, but you will save a whole lot of fuel, and gain a lot tougher forge.