Attaching soft firebrick

[Chris C]

Next step in this forge building process is installing the soft brick.  I've decided to stand my forge body on end and simply stack the bricks cut to size on all the side walls.  I then plan to build a collapsible "box" form to set in the center so I can pour the Kast-O-Lite in-between the box form and the soft brick.  After I'm finished with that and the application of the IR reflective coating, I'll lay the forge down on it's bottom.  I'm concerned the bricks might not stay in place when I do that.  Is there any reason I shouldn't use contact adhesive to apply the soft bricks to the wall of the forge to make certain they stay there throughout the fabrication process?

[Frosty]

It pains me to have to say this but some good refractory/ furnace . . . <GASP!> cement. Furnace cement is made to stick refractory masonry together and should do the trick. I believe you can buy it premixed in a can up to 3,000 f. 

Frosty The Lucky.

[Chris C]

He-he, Frosty, why does it pain you?  Is there something bad about refractory cement?  I'd only need to use it on the bricks closest to the ends.  I may not even need it if I cut my bricks so there's a slight tightness to the fit.  I just didn't want to go to lay this thing down and have some loose brick go sliding out.  Wait...........something just hit me.................I'll be covering the brick with KOL.  Does that really stick to the brick?  If so, the KOL liner ought to keep the brick from sliding.  Yes?

[Buzzkill]

Chris,

The pain is caused by the number of people who want to use refractory cement as a coating for direct flame exposure.  Most of the refractory mortars or cements will not hold up well if used that way.  However, they are made to stick bricks together, so your idea is sound.

Just a warning for both the cement and the kastolite. Porous dry bricks will suck the moisture out of the mix, so you'll want to "butter" the surfaces with water that will be in contact with the refractory mix.  If you don't do that you may end up with a "crumbly" casting or joint between the bricks. Kastolite doesn't pour very well when it's at the appropriate wetness for casting.  To make sure you don't have voids in your casting you'll want to use a combination of tamping the material and vibrating the mold form to get rid of air pockets. After that you want to maintain maximum humidity for the Kastolite to cure for a day or two then let it air dry (or use a low heat source like a light bulb) before firing to avoid spalling when water flashes to steam as it's heated.

[Chris C]

Hmmmmmm............"butter" the bricks.  I guess I could get them wet just before I place the square, collapsible form inside.  Will they stay wet long enough to force the KOL into the gap between brick and form?  This square tube is heavy. (too heavy, darnit)  I'm not sure I can vibrate it adequately. 

[Buzzkill]

If your inner form is porous (wood, cardboard, etc.) it will also suck moisture out of the mix if you don't have it coated with something impervious to water.   I don't know how long it will take you to set everything in place, and the ambient conditions will also affect how long things stay wet.  You may want to try a couple small tests before tackling the main project.

Frosty mentioned using a 3/8" drill with an "L" shaped piece of stock chucked up to create the vibration needed for his form.  It doesn't take as much as you might think to have the desired effect.

[Chris C]

I'm planning on making a plexiglass walled box for the forum, so it will not be absorbing any of the moisture from the KOL.  (I actually thought ahead for once!)

[Buzzkill]

I've never used Kastolite with plexiglass, so I don't know if it will stick to the plexiglass.  However, even if it does not, that's going to be a lot of surface area in contact and a lot of friction. Are you making the box so that the sides can fold inwards to help with the release?  When I've used a form with Kastolite it has generally been sonotube which I can just burn out after curing and preliminary drying is done.  Someone else may have better advice on release agents or form design to get good results.

[Chris C]

The material I have has a polyethylene covering to protect it from scratches.  I'll use angle iron in the inside corners and attach the plex to the corners with adhesive backed tape.  When the KOL sets up,  I'll just pull the angle iron away and the sides will be free to be pulled away.  I'm going to wrap the form with parchment paper and heavily coat it with Crisco, so I shouldn't have any problems.  (knock on wood)

[Frosty]

The plastic on the plexiglass should do the trick, maybe tape the corners so the KOL can't find something to get a toe hold on. The stuff is insidious. It WILL stick to parchment paper, I know. Saran wrap too. Did I mention its insidious? Grease it. . . Oh YES, grease it! 

Remember KOL is water setting it doesn't "dry." It behaves so closely to Portland cement concrete, that when it begins to set up you can get a little more working time the same way as with concrete. Once it sets, cure it JUST LIKE CONCRETE. It's much easier to find instructions on curing concrete than KOL and they're almost exactly the same. 

You are going to HAVE to mix it wetter than what the manufacturer recommends but we don't need anything like it's max strength so a little wetter is just fine.

Rod it in in lifts from the bottom. It'll stick to itself just fine but there's no way you can ram say 6" in without it keying and leaving voids you'll have to patch later. If the batch in the pot starts to set don't sweat it, mix up another one and carry on. It WILL stick.

Frosty The Lucky.

[Chris C]

Ed McCaffrey (a prominent knife maker) has practically been begging me to forget the square forge............forget the brick and just pour a 3" thick layer of Kastolite.  Says applying the KOL over the brick is a recipe for total disaster. I'm conflicted!

Here's what he said:  " Chris..... I personally believe you would be far better served with a round designed forge....especially if you intend to forge weld down the road. You'll have a far easier time learning, and your welding consistency will be far better. OK, that being said, to your question about castable thickness...... A LEAST 3" thick on any/all castable type refractory, otherwise you're just wasting your time and materials.

I've gone back, read, and re-read your post...... if I'm reading it correctly, your intent is to line with firebrick and then coat with refractory? If so, please don't go that route..... it will only be a few times firing/using it before it all starts to fall apart, then you'll be stomping and cursing it. PLEASE, if you're looking for usability and durability, rethink your design, and your materials. In the end, you're gona do what you want....I'm just trying to save you some time, effort, money...... and a whole truck load of grief."

This forge is 17" long.  Are you saying I won't be able to push KOL to the bottom of that with the forge standing on end?

[Frosty]

Sounds like Mr. McCaffrey is seriously old school. That much thermal mass would require a HUGE fuel bill. 

Were you using the old IFBs he's exactly right, they degrade rapidly at general forging temps and in one maybe two welding temp firings. Morgan Thermal Ceramics K-26 IFB is an entirely different refractory and is rated significantly above welding temps. 

Kastolite applied properly doesn't heat craze or check, I have streaks on a poker I used when lining the current forge and tried burning it off in the forge. The KOL streaks were hard to hot brush off.

The only real reason for a high thermal mass in a gas forge would be for annealing. If you need to do some annealing, bring a couple 3,000 f. hard fire brick to critical temp and lay your blade between them then close the forge up tight. A trick I used to use was heating a large steel bar to critical and wrapping the hot project piece and HOT bar in Kaowool and burying it perlite.

I've stopped suggesting folk keep large pieces of Kaowool at hand since learning about the breathing hazard it presents.

Frosty The Lucky.

[Chris C]

Thanks, Frosty, I'll take your word over his.  He argued with me for week over the makers mark I wanted to use on my carving knife blades because it didn't have my name, city and state on it.  Where in creation would I put all that on a 1 1/2"x .375"  blade???

I sent you a pm you've not responded to.  I know Alaska is a long way from me................Did it not "get there"? 

[Frosty]

Now you're just being argumentative Chris, there's plenty of room for that in a 1.5" x .375" space! There're two sides too, you can include your mailing address and phone #. 

You do fine wood work make presentation boxes for your blades and carve your contact info on the inside of the lid with your maker's mark as a graphic so folk can connect the box and knife that fits in it. 

Frosty The Lucky.

[Chris C]

He-he...............carvers aren't at all interested in presentation cases..............they just want to carve with it.  Now when I start making full-sized knives, I'll be doing that.............mainly because I don't want to have to take of leather work as yet another hobby! 

Argumentative?  Yup...............at the end of the disagreement I told him I'd try to find a place for my blood type on the blade.  Don't think he found the comment humorous.    I just get ticked with people who think their way is the only way and you can't possibly accomplish what you want to do if you do it a different way.  Heck, we'd still be flapping our arms trying to fly if someone hadn't said "That's nuts, let's cobble together a flying machine!"  Oh well, you get my drift.  Nothing in this world is chilled in stone.

[Frosty]

On 6/27/2019 at 11:33 AM, Chris The Curious said:

Heck, we'd still be flapping our arms trying to fly if someone hadn't said

"Stop that nonsense Oog, my head itches climb back up here and groom my scalp!" 

"Isn't the way Oog flails his arms funny when he falls off a limb, Gronk?"

Frosty The Lucky. 

 

[Airhog]

I realize I'm a little behind on this topic but I was thinking of using a mixture of perlite and white portland about 2inches for the insulating layer on and 18 inch pipe then putting about an inch of KOL30 then a reflective coating on top of that. My biggest question is would it be feasible to put the KOL30 on top of the perlite and portland mix and it not crack? 

[Frosty]

NO! Portland cement will spall far below forging temperatures. Portland cement in a propane forge is not only a poor material it'd outright dangerous. In your proposed configuration you couldn't even shut it off when you discover it's blowing itself to pieces, the KOL WILL keep getting it hotter until there's nothing left to pop.

Don't try to invent this stuff, use an established refractory, it's much more economical. So, you save a few dollars or whatever form of money you use using cement and perlite. Steam pressure is going to cause it to spall UNLESS you have it contained, maybe you do a REALLY good job applying the KOL so it's contained. It won't spall, pipping bits and pieces of HOT concrete around your shop, it'll maybe build up enough steam pressure to justify the term EXPLODE and blow chunks ann inch thick and a couple wide around the shop at a few hundred MPH, maybe remove appendages or just poke holes in folk in the shop. 

Let's say you don't send anybody to the hospital, doctor's even or get to enjoy the pain and suffering of having a handful of corn kernel sized pieces of HOT concrete on your hair, down your shirt/shorts/shoes, etc. You luck out the forges just keep crumbling. Doesn't really matter, it won't make a working gas forge.

Of course you will have learned a lot by time you just follow established plans and build a functional forge. If you choose a proven set of plans and FOLLOW them you'll build yourself a working forge and we'll help. 

Frosty The Lucky.

[Airhog]

See this is where us newbies need further instruction. I have talked to several people who supposedly know what they are doing  and advised me that if I used straight perlite and just enough white portland to make the perlite stick together that that alone would make a good insulating band between the steel and the KOL30. I was just looking for a castable that wasn't so expensive to use as an insulating blanket instead of using the ceramic Kaowool which I really don't want to use because of health reasons. I would have fired the perlite enough to extract the water from the mixture before applying the KOL on top. 

But you are correct in the fact that I was talking to people that was making their own refractory to save the expense of using all KOL30.

 

I will add that those people were not on this board. 

[Mikey98118]

Perlite mixed with refractory, or less expensively with furnace cement, has been successfully used as a SECONDARY insulating layer, outside of a good semi-insulating hot-face layer in various heating equipment since the sixties; it is also glued together in such monolithic forms with sodium silicate.

[Irondragon Forge ClayWorks]

Not knowing where in the world you are located it's hard to give advice on where to obtain supplies. Hence the suggestion to edit your profile to show location.

Have you read this yet? READ THIS FIRST

[Airhog]

Thanks Frosty, Mikey and Irondragon for the advice. Chris the Curious I will get off here because I wasn't intending to hijack your thread. 

[Mikey98118]

Why not? He can always hijack it right back

[Glenn]

Moderators have been known to split a thread into two new threads when needed.

To avoid hijacking a thread, start a new one. (grin) 

[Jonah k]

My forge is made of insulated fire brick and I just friction fit it together. It is held together tight by putting angle iron on the 4 edges and then I have pallet banding ratcheted down in 4 spots. Only down side is you need a pallet bander. But it seems to work good and has held up for about 5 years so far. I have a piece of hard fire brick In  the bottom that I change out every once in a while to stop the flux from eating the bottom too much. You can kind of see the idea in this picture.

HERE IS A BETTER PIC