Refractory on top of Soft Bricks.

[Chris C]

I'm still in the planning stages on my forge.  I've asked a lot of questions on different forums and have done searches until I'm blue in the face.  (yes, I'd done the off-site site search here)

I'm planning on using soft brick on my square forge.  While I may not ever get to the point of doing forge welding of billets, I don't want to build a forge that's not capable of it.  So I'm thinking of coating the soft brick with refractory material.  Good plan....................or not?

[MonkeyForge]

Good question. I have been considerering this myself in the past. In theory a castable layer inside a soft brick forge would take 1) the direct flame contact, 2) prolong cool down time after shut off. (If thick enough)

Whether or not point 2 will prevent degradation of the brick due to thermal shock is the interesting question.

Of course different kinds of bricks have different properties when it comes to resisting thermal shock, I think some people with more recent experience on that will chime in.

Long story short: potentially good idea.

Maarten.

[Mikey98118]

Did you run across mention of Morgan's K26 highly insulating hard bricks?

[Frosty]

The recently developed Morgan K 26 insulating fire brick has a working max temperature rating of 2,600 f. and holds against rapid thermal cycling so works well in a propane forge, Though sometimes a home built burner will exceed their margin and they'll degrade. Dr. Frankenburner's latest creations may make us find higher temp refractories though.

However a layer of Kastolite bubble refractory keeps the IFB out of direct flame contact and reduces the absolute temperature conducted to the IFB. With heat transferring into it more slowly it has more time to dissipate it through and out so the environment is more survivable for the IFB. 

A zirconia kiln wash performs in a similar way, lower thermal conductivity means it holds more heat and so has more energy to radiate back in the forge. Unfortunately it radiates heat in a sphere but it slows the transfer to the Kastolite which again slows transfer to the IFB. 

Just for reference K 26 IFB has a (supposedly indefinite) max working temperature of 2,600 f. And 8lb. Kaowool has a max temp of 2,300f and degrades. Kaowool is also a Morgan Thermal Ceramics product.

The effectiveness of a hard refractory inner liner say Kastolite 30 saving Kaowool in a forge is a known factor here. My shop forge has lasted for years.

So, yes a layer of hard refractory over Morgan K 26 IFB should work a treat, I'm watching some the club built to see how they last and maybe stop using Kaowool unless I have to.

Frosty The Lucky.

[Another FrankenBurner]

If you do attempt this, please keep us filled in.  I have been wondering the same thing.  When I get the time, I will be testing a few different refractories on the bricks in the hopes of armoring them enough to survive as baffle walls for my forges.  

[Chris C]

I'm listening.  Remember, I'm a total newbie.  What (little) I know comes only from what I've read because I've no personal experience.  I've only attended 3 of the Thursday night open forge events our group holds.  What I have learned from those visits is I do not want the batten type insulation.  I definitely want the soft bricks.  I'd really like the K28 bricks if I can find/afford them. (I know the K26 will work, but I think "bigger is better", in this case)  But I hope some day to perform forge welding and have read enough to know the flux used does damage.  That's why I'm wanting to coat the bricks.  Any comments are appreciated. 

[Another FrankenBurner]

I have broken several of the K26 bricks but several people have reported good results using them.  I was planning on coating them in plistix 900F.  I only use them for baffle walls.  I like the ceramic blanket, refractory, wash route for forge building.  

As to the forge welding, I slip a thin high alumina kiln shelf into the forge when welding.  The flux melts into a goo puddle in the bottom of the forge which is sticky and you stick your irons in it.  It's annoying.  After I am done welding, I can remove the shelf and no more flux in the forge.  

[Chris C]

That's a great idea.  I'll write that down.

[JHCC]

11 hours ago, Chris C said:

What I have learned from those visits is I do not want the batten type insulation.

Why not?

[Chris C]

I've only used a forge for three evenings.  I can only state an uneducated opinion.  I noticed the interior of the forges were torn/tattered and the floors (being of the same material) were pretty much destroyed.  I would prefer a hard firebrick floor that could easily be removed and the rest of the forge insulated with soft brick coated with a higher heat refractory.  The forges I've seen on Youtube presentations that had such a setup made more sense to me.  Once again, an uneducated opinion.

[JHCC]

Ceramic wool on its own is a real problem. Not only does it get torn and tattered, but you get bits of ceramic fiber getting into the air, which can get into your lungs and act like asbestos. Not good. The best thing is to rigidize it and give it a layer of hard refractory.

Also, as noted, hot flux eats ceramic wool for lunch. Again, a flux-resistant floor (either a hard refractory shell or a piece of kiln shelf -- or both) is the way to go.

I haven't seen the forges where you've been working (and I'm certainly no expert), but from the sounds of it, you shouldn't use them as examples of what ceramic wool-lined forges can and should be.

[Chris C]

Fair enough.  But is there anything wrong with choosing a soft brick interior?

[JHCC]

For that, I defer to Frosty & Mikey.

[Frosty]

See my above post for a short how to. Brick pile forges have a lot of advantages, we've discussed them in depth in Forges 101.

Frosty The Lucky.

[Chris C]

Thanks, Frosty.  I think I'm on the right track.  Gathering materials for my forge build.

[Mikey98118]

11 hours ago, Chris C said:

I noticed the interior of the forges were torn/tattered and the floors (being of the same material) were pretty much destroyed. 

I really like YouTube. After twenty years designing burners and forges, separating the wheat from flax is just  reflex. Too bad about all those newbies trying to choke down a bowl of flax, but that's life...

[Chris C]

I've been in manufacturing and fabrication most of my adult life.  I can usually sort out the chaff.  When I'm not quite sure, I do a lot of searches, reading and asking questions..............lots of them.  I research most everything I get into until I'm almost sick of it because I just plain can't afford to have a "closet full of slightly used holsters", as they say.  Easier to sort out the various suppliers, ask questions, make decisions and then make a purchase.  I'm pretty sure I''m headed in the right direction on this build.

[Another FrankenBurner]

Hopefully you avoid the "slightly used" part but it seems making more then one forge is in the cards for most.  You build one and immediately think "next time I will..." and/or you use it for a while and come up with some reason to need/want another.  

The best advice that I see routinely is avoid the thought "I will build one forge and I will build it big enough that I can make everything I can ever imagine making."  This usually ends in a disgustingly large forge which is not hot enough or uses so much fuel that it is very quickly abandoned.  

Using bricks allows internal volume to be adjustable which is very nice.

We recently built a forge which is 185 in³ and it has become my favorite for general use.  Now we are planning a forge at 50-75 in³. We also have a 150 in³ and a 450 in³.  The 450 only comes out to play when it has to.

[Mikey98118]

17 hours ago, Another FrankenBurner said:

I have broken several of the K26 bricks but several people have reported good results using them.  I was planning on coating them in plistix 900F.

With your burners, that is what is needed.

[Chris C]

Sorry for not responding sooner.  I 've been off-line since last Thursday with computer problems. 

Thanks for the comments in this thread.  They've been very helpful.

[Frosty]

WHEW Chris that was CLOSE! We were about to send out the brunos to rough you up for not responding quickly enough. 

Actually I don't think anybody noticed, we had an excuse to talk so we're good.

Frosty The Lucky.

[Chris C]

Whew, it's always encouraging to know nobody noticed I was missing.

[Frosty]

That was AWFULLY quick, are you stalking us or peeping?

    

Frosty The Lucky.

[Chris C]

Stalking, of course.

[Frosty]

Uh HUH, Chris socks it to us! 

Frosty The Lucky.