Greenpatch 421

[Dodge]

Anyone ever use it?

I'm planning a new gasser to replace the giant heat sink I've been using; 3" thick castable walls. It has served me well enough, and I have learned a lot with it, but due to its poor insulating qualities, its a terrible gas hog. Time has come for an upgrade and my goal it to do it as cheaply but effectively as possible. I want a forge with good insulating properties but also be able to stand up to some mild abuse. This time I'm going with ceramic wool; Inswool specifically which I got a very good deal on, and the shell is a piece of 10" pipe x 15" that was salvaged from a nitrogen bottle. I will use fire brick for both ends. I may reuse the venturi burners from the other forge but new flares will be needed as they had turned to brittle scale and crumbled upon removal. I know the most desirable method is to coat the ceramic wool with ITC100 or equivalent. However, I am trying to avoid the use of the ITC product because:

1) Its expensive (I know that

[brucegodlesky]

Dodge, One thing I would do is have a floor of either poured refrac or firebrick. That will keep any flux from destroying the ceramic wool lining.
The GP421 sounds like the ticket for coating the wool.

[Woody]

There used to be some stuff called Macote that worked as well as ITC 100 but I have been unable to find it lately. I have mixed a 3000 degree refactory cement to a thin slurry and applied that to my new Kowool lining it seems to work well and is holding up good and I can reach welding heat with no problem. I don't know why the Greenpatch wouldn't work just as well.

[Dodge]

Bruce, I do plan to use something hard for a floor. Not sure if I will use brick, or maybe a thicker layer of ths Greenpatch stuff, or see if i can get a small amont of castable from the same source as my Inswool. I was able to catch they guy just after they had done some contract work and had some good forge sized scraps he sold me real cheap. Maybe get lucky again

Woody, I had thought about a slurry such as you described also but wasn't sure how it would hold up. The refractory guy (Same guy that sold me the inswool) warned me when I mixed the refractory (2600

Edited March 9, 2009 by Dodge

[Frosty]

You're plan should work alright. Though I have no experience with the specific product the specs sound good enough.

The reason you were warned to use as little water mixing up the castable is two fold. First is shrink checking, the more water the more it'll shrink as it dries and the more it shrinks the more it'll check. (crack, think dried mud puddle) Also, water replaces the refractory, there must be some to act as a lubricant so it can be poured, rammed and shaped and also to activate the hydration cycle that sets it. However if you use too much water the refractory loses density and durability, heat rating and thermal cycle strength.

What you want to do is coat a ceramic blanket and this is a whole different kettle of fish with a different product. I'd say go for it there isn't much to lose if it doesn't turn out well. I've coated Kaowool with kaolin slip with good results in the past and still dip my burner nozzles in it to extend nozzle and tube life.

Also, coating the ceramic with slip won't prevent you from coating it with ITC-100 at any time in the future. Just make sure the interior surface is in good shape so you're not wasting the ITC-100 on flakes.

If you think you'll lose too much interior space by making a double wall forge you can always use SS stove pipe for the shell, it works a treat.

Sounds like you have a good workable plan.

Frosty

[Steve Sells]

Dodge, FYI the ITC-100 does NOT go over the inswool, its only to be used as a top coat, the inswool still needs to be sealed first. So you wont need as much of the expensive stuff after all, if you decide later to add it, so Go have some Soup. :D

[Dodge]

Steve, I thought I had read about people painting the ITC directly on the wool. One description, IIRC, even recommended wetting the wool a bit with a spray of water so the ITC wouldn't get drank up by the wool as fast. Never the less, one of the sites that sells the GP 421 had a testimonial section and one person did in deed use the ITC over the GP. I can see the merit there. However, at this time, it would defeat my secondary goal of getting this forge up and running with as little monetary expenditure as possible. (OK, it's my absolute main concern!!) I'll have chowder please :D

[Frosty]

You can most certainly use ITC-100 over ceramic blanket and it'll even go a ways towards sealing the fibers, that just isn't what it's for.

If you don't wet down the surface before applying ITC-100 it dries on the surface before it can form a bond and will flake off sooner than later.

You have a solid workable plan Dodge. It can be tweaked for higher performance later on.

Frosty

[Woody]

Dodge

I dried my slurry for about a week before I fired the forge, it's cold here so I put a trouble light in the forge and left it on.

[Steve McCarthy]

Dodge, I have used Greenpatch quite a bit in the fireboxes of wood fired boilers. Max temps were only around 2400 deg. We used it as morter and also to skim over the top of cracks to keep ash out while the refractor walls expanded. It has served me well and is a tough product. If thinned down with water, or if applied more than about 1/2" in thick, it will crack as it dries. I know you got the greenpatch free, but Plastix 900F would work better for coating the insulation. 900F is not as tough but is much easier to apply.

[Dodge]

Thanks all, for your input.

Steve from Huston, I'm sure I will have to thin with water so anticipating cracking, I thought I would try a couple thin layers with the second layer to "patch" cracks from the first layer. I got nothing to lose at this point. Having never opened this bucket, however, I don't know what I'm in for anyway. I got it a couple, maybe 3 years ago. It was probably fine then, but it has since, sat in my garage. I could possibly have a plastic coated brick LOL. Then I will have to re think my low buget plan

Scott

[Dodge]

I did a little experimenting today. I opened the bucket that I've had for, near as I can recollect now, at least 3 years. I don't have any idea how old it was when I got it so I had no clue as to what I was going to find. There was a very thick mass covered with a thin puddle of brown liquid on top about the color of maple syrup. This liquid dried to a sticky consistency when rubbed between thumb and forefinger, so I assume its a sort of bonding agent that had risen to the top as the mortar settled. I got it all blended pretty good after about a half hour of mixing I then took a small amount and added enough water to thin to a paste I could spread on a scrap of Inswool that I had moistened with a spray of water. The paste was about the consistency of a milk shake and the Inswool scrap was 2" thick x about 3" x 8". To speed the drying process, I put it in the oven at about 250 degrees F. My main goal was to see how rigid the Inswool would be with a coat of the mortar. There was some cracking in the drying process, but there appears to be some fiber like substance in the mortar so I'm not overly concerned. It seems to have good adhesion, which was another reason for the test. After I removed it from the oven, the mortar is quite hard. I didn't test to failure but I can tell that it would take some effort to poke my finger through it. This layer is probably 1/8" and when I actually line my forge, I will most likely apply two coats to insure the durability. The pictures were taken before it went in the oven. I will update this thread with some field testing when the forge is built. What I need to do next is decide on the configuration of the shell; vertical or horizontal. Vertical, I don't need to buy any fire brick or ceramic shelving; I just need to cut pass through holes in the 10" shell pipe and I won't need the full 15", but the length of material I can heat is limited to the inside diameter which will be 6". If I go horizontal, I'll want end doors of some sort at least for the back and some sort of floor. I have considered simply spreading an extra thick layer on what will be the floor, say 1/2" thick. I don't know how this stuff will be affected by flux, but I have enough mortar to do lots and lots of repairs And I could even make the doors out of Inswool framed with metal and coated with mortar, so I reallly don't need brick at all. A third alternative is to make a convertible that can be horizontal or vertical to meet my level of insanity at the time (Insert "Thumbs-Up" emoticon here )

Edited March 16, 2009 by Dodge

[Frosty]

Looks pretty good to me Dodge.

I'd be tempted to thin it even more so it'll soak into the Insulwool for the first coat, then make the second thicker. Intuition is telling me if the first coat actually penetrates the blanket 1/4" or so then the second coat will bond better and maybe be less likely to shrink check as it dries.

Just a thought though.

So when are you going to put the flame to the test piece?

Frosty

[Dodge]

Pre-occupied for the next couple weekends, but if I can find the time during the week, I may try to torch it into submission with my Harbor Freight propane weed burner :D

[Dodge]

Well, I managed to get a few minutes to myself this evening and fired up the wed burner. I know, Right? They don't get THAT hot but I did make some observations that seem promising. Most important, I didn't burn the house down And while I only blasted at it for a minute or so, it got it too hot too touch without a glove. The side with no mortar was, as one would expect, hardly even what could be called warm. What I gleaned from this test is that a similarly lined forge should absorb considerable heat in the mortar layer and hold it there due to the Inswool. With a layer of about a 1/4" to 3/8", I should end up with a fairly durable yet well insulated forge.
Ready,,,Begin!! :D

[Frosty]

Sounds good so far.

Do you know anyone with an oxy/acet torch? A couple minutes with it will tell you if it'll take the heat. If it survives even 30 secs or a minute under the torch without vitrifying it'll be good for propane forge temps.

Frosty

[Dodge]

I do have O/A. Weed burner was just easier to get to lastnight According to the spec sheet I found on-line, GP421 has a 3200

[brucegodlesky]

Dodge, the first fgorge I built from poured refrac was heated with a HF weed burner.
Sounded similar to ajet engine but got hot enuff to Heat treat anyhow.

[Dodge]

Did the O/A test tonight. If I had any doubts, they have faded to black :) I aimed the torch (a small welding tip. Victor Type 1, Size 1) over my test piece about 3" or 4" away for about minute and a half to maybe 2 minutes. If I stopped oscillating it would get too bright to watch. Took pics with my phone's camera. Little hard to handle torch and commit decent photography but the pic is about 10 seconds after I took the torch away. After about a minute, I turned it over and I could touch the bare Inswool without a glove. It wasn't even warm. Went back to it about 15 minutes later and the whole test piece was cool to the touch and aside from some discoloration, the mortar was unscathed. If anyone cares to see the video, here is the link to its location on Photobucket. Its only 50 seconds but I was having trouble multi-tasking LOL VID00006.flv video by DodgeForge_photo - Photobucket

BTW, Frosty. I believe your right about letting a little more soak in to the wool. After the exhaustive testing the piece has undergone, I see it isn't as thick as I thought and its getting kinda banged up and, I can see that where I poked a screw driver through, its just holding on to the outer fibers. I will get the first coat a little wetter to aid in the bonding.

Edited March 18, 2009 by Dodge

[Frosty]

Sounds to me like you have a go for launch!

I was surprised at how wet I had to get kaolin slip to get it to soak into Kaowool at all. I thought it'd soak it up like custard into french toast but it just lay on the surface for the most part. Wetting the blanket helped but not a lot.

I ended up doing something else, namely the double liner so never did find out how thin I'd need to make the slip to get decent penetration. I figured 3/8-1/2" penetration would make it pretty bullet proof. Still, I never got to it so I await your reports with bated breath. . . Well, okay, I'm really interested.

Frosty

[Dodge]

Well, Its finished! I made the floor by making a 3/4" thick x 5" by 14 1/2" form from cardboard and then filled it with the Greenpatch. After putting in 2" of Inswool, I spread in a good layer of the Greenpatch mortar to mold it in. The after drying, I applied another good coat. I think I have about an 1/8" thick armour. The floor bulged during the first test firing. Not sure if it wasn't fully cured or the layer of mortar just separated from the slab I cast. After the first real run, the bulge collapsed and there was some significant cracking throughout. I "glued" one loose piece back in with some thinned mortar and repaired a lower corner of the front door (I think I gouged it with an odd shaped piece I heated for a work rest). I'm not real concerned with the cracking, however as it still seems to be doing is job, and after firing, it's like rock. In fact, the piece of floor I repaired sounded like ceramic when I tapped it against the forge stand. The forge heats up in about five minutes at 5 PSI or less with the blown 1.25" burner I built. The stand is salvaged from my old forge. I tossed the shell and knocked the castable out of the base so I could run my blower up from below with as little sticking out past the frame as possible. If anything was to hang out, I didn't want it to be burner parts. As it is, there's a happy medium. The pieces that cradle the shell were salvaged from another project that used the same pipe as the forge shell. I plan to make a permanent mounting for the fan also. It isn't pretty but it works! Criticisms and otherwise are welcome :D

[Frosty]

It looks good and hot to me. Do you like it? I think that's what counts.

Frosty

[JamesBBrauer]

I followed this with interest since as of 2am last night I have a kaowool lined forge that needs to have the insulation stabilized or encapsulated. I was going to start with a kaolin liner like is described here. It looks like I might be able to get kaolin clay locally as they sell if as unscented baby powder, or drive down to Denver for a bag of the stuff. But on to my question.

I was going to slather a thin slip onto the kaowool. Do I need to follow a firing schedule like with a castable refractory, or would drying it out good with a space heater do the trick?

[Frosty]

You'll need to dry it slowly and fire it in stages.

A forge comes up to heat pretty quickly and unless you give Kaolin a chance to dry completely and bisque fire a little you might get spalling.

I'd make sure it's good and dry, maybe hang a light bulb inside for a few days rather than a space heater. I suppose it depends on what you call a space heater come to think of it, here they're kerosene of diesel fired jet engine looking things that blow a lot of hot air. Really hot at the throat, too hot for refractory drying.

Anyway, once it's good and dry I'd fire it for maybe 2-3 minutes depending on your burner, definitely NOT get it to red heat. Then I'd stuff some kaowool in the door and let it cool. Any moisture should escape through the burner opening.

I'd then fire it for a few more minutes or if you can turn the burner as low as it'll go and burn stably longer at a low red. If you can hold it at low red half an hour would be excellent. After that you should be fine turning it up and using it.

That may be overkill but sometimes it's easier to take it slow and easy and not risk losing a bunch of work.

Frosty

[Dodge]

Yes, I like it a lot Frosty! It has surpassed expectations! Only thing I'd do different next time (if there would be a "next time" ) would be to try to dry it slower and more thoroughly before firing. Many factors could have contributed to cracking here. Most of it occurred during drying. One: the mortar has been in my garage for at least 3 years albeit, factory sealed. Two: it may have froze at least once. I don't know if these are negative factors, but like I say, it works great so far :)