Skamol Kiln Advice

[Garner Britt]

Hey all,

I'm thinking of building a Skamol front loader based on Henry's latest Glass Notes. It will be used for annealing and an occasional fusing or casting. Max temps about 1600f. The hot face will be 2" of V-1100 backed with 2" of S-Isol

I'm very impressed with the thermal data on this stuff but have a few concerns about long term durability.

Anyone have any advice? Dos? Don'ts?

garner

[Scott Dunahee]

I've been running my front loader built from skamol for 3 years now. The top loader is on 2 years and they both look new. They hold up fine. I used the skamol as the roof of my front loader, unsupported except for three sides and it hasn't moved at all.

BSD

[Garner Britt]

Scott,

Good to meet you a few weeks back. I wish I would have looked more closely at your ovens. Do you ever do any casting in either of them? Am I also remembering that your pipe warmer was Skamol too?

garner

[Scott Dunahee]

I haven't done any casting in them. I never take them above a thousand degrees. I could cast in the front loader if I wanted, but I think it'd be underpowered. I takes about 45 minutes to hit annealing temp from room temp and an hour until it's stable. That's with 2" of fiber behind it. It takes 26-28 hours after I key "run" until I can open the door (below 200 inside). I run a 10 hour cycle, including 1 hour soak, down to 450 then it coasts to room. It's 3 phase, 28 amp draw so it is about 10 kW for a 2' cube. That's 1250 watts a cubic foot, I'd guess so it may be all right, but I use it as an annealer primarily.

My top loader has some mild steel parts inside (for various reasons) and I won't run it higher than 1000. The steel is fine in that range.

The pipe warmer just has a skamol roof. No reason it couldn't have been all skamol, but I reused the bricks from the previous, and much more inefficient, pipe warmer I had.

I know that Donovan Brooke, who used to own a studio just south of here, used skamol to reduce his glory hole door size by just hacking a piece onto each side of his barn doors. That did degrade. He probably reduced the total size of the opening 4" diameter, so a 2" arc per door was exposed skamol. I know he was still using the first pieces he installed when he sold the shop but they were looking rough. Worked fine, but looked like hell. I believe he got 18 months out of those door reducers.

The stuff is rated to 2100 continuous with direct flame contact okay as long as temperature is taken into account. After a year in service, the roof of my pipe warmer where the flame splashes looks no different at room temp than it did when installed. I run the warmer at around 1000 measured in the front crown area (there is a 3" crown above the door opening) and I bet the skamol where the flame is splashing is at least 1500. I'll try to remember to stick a thermocouple on a stick into the box when it's running to check.

It was really great to meet you too. Thanks for the beer!

BSD

[Garner Britt]

I haven't done any casting in them. I never take them above a thousand degrees. I could cast in the front loader if I wanted, but I think it'd be underpowered. I takes about 45 minutes to hit annealing temp from room temp and an hour until it's stable. That's with 2" of fiber behind it. It takes 26-28 hours after I key "run" until I can open the door (below 200 inside). I run a 10 hour cycle, including 1 hour soak, down to 450 then it coasts to room. It's 3 phase, 28 amp draw so it is about 10 kW for a 2' cube. That's 1250 watts a cubic foot, I'd guess so it may be all right, but I use it as an annealer primarily.

It surprises me that at 1250 watts per cubic foot, it's kind of sluggish. I assumed that one major advantage is the lower thermal mass of the skamol products compared to IFB would equal quicker heat up and cool down....

My insulated IFB top loader is of comparable size (9 cubic feet) with 9kw of power and it comes up pretty quick...

No one else has used this stuff?

garner

[Asa Shows]

I have used Skamol vermiculite and calcium silicate boards an annealer. The stuff is nice to work with and although I have only been running it daily for a year, it has held up well so far.

I used 2" of the V-1100 (475) for the hot face and 2" of the S-1100E for backup. Its interior interior is 3'4"x1'8"x1'8" for a volume of 9.25 cubic feet. I had to fit under 30Amps @ 240 single phase and I think with the wire I had on hand it ended up at 6.2KW. Giving me .67KW a cubic foot. It takes about an hour and a half to get up to 975 or so. It isn't 100% power until around 650F or so when the ramp rate exceeds the elements ability to keep up (if I made the ramp more agressive, it might reach temp in an hour). If I recall correctly, it idles at 3.0KW or so. I fused with it once and it took forever (ok like 4 or 5 hours) to hit 1450F, definitely underpowered for that. Coming down from 975 or so, I soak for an hour and then ramp to room over 8 hours. I don't know how much it kicks on during this since I am always gone. When I get back the next day (14 hours or so), it is usually around the lower 200's temperature wise.

Stuff is very nice to work with from a building perspective. It is dense, both the vermiculite and the calcium silicate. The vermiculite I have (475) is 30 lbs/cu foot while 2300F brick from thermal ceramics is around 32 lbs/cu foot. The calcium silicate is 15 lbs/cu foot which depending on the density of fiber you use, is 2 or 3 times more dense. Definitely the reason it comes up and down slow. Not really something that is good for fusing. The power consumption at idle is more than I calculated it should be. The things I have made with fiber and brick have been much closer to what I calculated. Not sure whether the Skamol specs are idealistic or whether it is in some detail of my design.

Long and short, it works well as an annealer. If I did it again, I'd probably still use the vermiculite face, but I'd back it with fiber. If I did something for fusing, I'd make it all fiber except the floor in order to move between temps quickly.

[Garner Britt]

A little update on the kiln I've built.

I used v-1100 (600) and S-Isol backup. I used 2" and 2" for the walls and roof and 1" V-1100 with 3" S-Isol for the floor and doors. Just trying to save some weight and improve insulation in the areas that didn't get element grooves.

I've found that the stuff expands and contracts quite a bit. The way the doors are framed basically sandwiched the boards between two angle iron frames. After the first test up to 1600f, the panels in the doors cracked. Not a huge deal but, I should have given it a bit more room to move, maybe used some frax to create a soft border that would allow for more expansion.

At 1250 watts/cubic foot it gets to 1000 in about 40 minutes, not a rocket, but I think it's reasonable.

This stuff is a dream to work with as it can be treated like particle board. Cuts, dados, routes like a charm, though very dusty.

I'll try to link to some photos when I take them.

thanks for the advise

garner

[Jordan Kube]

I agree with Garner on the sluggish numbers. I've built a bunch of annealers in a bunch of different sizes. It seems like brick or fiberboard would do better. Is skamol cheaper or something?

[Garner Britt]

Jordan,

In short, yes Skamol is cheaper than brick and a lot cheaper than fiberboard (unless you've got a good source). I can also drive 2 hours to pick it up and not pay shipping.

I used it out of curiosity and it's super easy to build with. I'd do it all over again but I'd use 2" V-1100 (600) for the doors

I'm not a big fan of fiber board especially if I have to cut it and groove it for elements (I'm getting itchy just thinking about it)

I think the thermal performance is about the same as IFB. The density of the Skamol products seem to be what makes them kind of sluggish.

garner

[Marty Kremer]

No Vboard kiln yet- it's still in the planning stage but I've been using the 2" med. density (475?) for kiln shelves for several years and they hold up reasonably well. We do have to be careful about abrasion and the kiln must be vacuumed for dust before every firing. Top temps around 1600, usually to 1480 and held for up to 2 hours.

I tried the stuff on the floor of my brick kiln and found slight warping and some cracking- could be from the weight of the shelves and glass on top.

Interesting about the expansion- I'll have to check Skamol's data. BTW, I was told that Jim (who ran the NC office and was very helpful) is no longer there.

[Garner Britt]

BTW, I was told that Jim (who ran the NC office and was very helpful) is no longer there.

Jim runs a company called Southern Services which is a Skamol distributor. He'll sell you what ever you need where as the Skamol office will only deal with full pallets....Very helpful guy.

btw, very nice work Marty

garner

[Holly Wallace]

From Marty- the kiln must be vacuumed for dust before every firing.

This may be a stupid question, but would a "tent top" of fiberglass under the top elements stop particulate dust from falling on the pieces below?? Would it withstand the heat? or block the heat too much?

[Marty Kremer]

The lid isn't the problem, it's rigidized fiberboard with the elements suspended in quartz tubing.