A frame inside a furnace?

[David Patchen]

I need to keep small crucibles in an electric color pot stable and arranged under their respective gathering ports. I've considered a couple options, but none seem ideal so I thought I'd get this group's thoughts.

1. Use softbrick wired together with nichrome to form a square, then routed to fit each crucible. However, I fear the nichrome wouldn't offer much strength at temperature and the softbrick would provide insulation to the crucible, which would slow its heating. Not good

2. Weld up a metal frame the crucibles would slip into. Question is, what would be able to withstand heat cycles up to 2000F? Stainless?

3. A frame of routed kiln shelf - but this would still need to be wired to a stand and given stability. I have kiln cement--could I use this to create a frame of routed kiln shelf and softbrick?

4. Use upside down flowerpots, with the bottom hole opened up to snugly fit one of the crucibles (5" wide). The flower pot would become a stable stand. But would these destruct after a dozen heat/cool cycles? It would really suck for it to fail while holding a full pot of color. Ouch$! Me$$

The color pot furnace is only going to be used on a daily basis, so up in the morning (or overnight) and down at the end of the day. What do you guys think I could use to secure the crucibles? thanks!

[Brent Hickenbotham]

How big is the furnace and with what dimensions are you working with? Do you have a picture? what crucibles? 15, 30, cylinder, bowl?

[Jordan Kube]

What are you gonna be doing to these crucibles that you need this support? Are they really narrow on the bottom or something?

Metal is out of the question if you want any kind of longevity.

[Tom Fuhrman]

I've known people who put the crucibles in the furnace and then poured about 2" of sand around them. It keeps them in place and absorbs the glass should one break. also catches stringers so they can be easily removed when furnace cools.

[Drew Fritts]

David,

1. Unless it can be totally protected from pops and drips, the soft brick is a bad idea because it will dissolve when glass gets on it for some reason, leaving the crucible unsupported.

2. The metal frame idea won't work either. The metal will anneal over time and sag. It will also scale badly - yes, even stainless steel. The scales can actually pop off and into the pot. Trust me on this one.

3. The flower pots will deteriorate rapidly - after only a few firings.

4. The kiln shelf idea will work, but it's really hard to "route". Another idea along the same lines is to go to a pottery supply and get some kiln furniture. I've built my plinths (crucible stands) from 2" x 2" x 6" kiln furniture posts (on their sides) and they work great.

If what you're trying to do is keep the crucibles upright, why not something like kiln furniture posts over quartz or mullite rods. You can hang the rods with your nichrome wire after slipping the posts over them. I wouldn't use just the quartz or mullite rods by themselves because they will stick to the crucible if any glass comes over the side. With a kiln furniture post protecting the rod and the post touching the crucible you could always just replace the post if it got stuck. They're cheap!

Drew <+><

[David Patchen]

It's a modified 18" x 18" kiln that's loaded with really little (4.6" diameter x 6.5" high) cheapie assay crucibles. They don't have very wide bases, thus my concern. I'll be dipping in them from directly above and want to make sure they don't move around.

[Richard Huntrods]

If you cement the soft bricks together with something like "Super Titebond" mortar, it will hold up at furnace temperatures. After making the place to hold the crucible, either paint on a coat or two of the same morter thinned with water or dip in the diluted mortar. This stuff forms a glass-like barrier to slow the erosion of soft brick with glass.

OR - make the shape you want to hold the crucibles with rammable. This stuff resists glass erosion pretty well also. Duquesne Thermogen 85 should work OK.

OR - use a high-alumina castable like Fractocrete 3400 or Greencast 97 to cast the shapes you need.

Because this lives in the furnace, I'd probably opt for the rammable or the castable, depending on your construction preference.

OR - if your furnace design works with it, just pot them in grog. This would depend on the height of the lowest coil off the bottom.

Cheers,

-R

[Brent Hickenbotham]

David all you need to do is get some castolite 30. make a form out of wood a little smaller than the kiln, find something the diameter of the crucibles and cast the imprint into the castolite about 2 inches deep and give it about an inch to an inch and a half base to the casting. it should work beautifully and cheap with nothing to break except the pots or castolite. wish I lived closer I could make you one in 30 minutes.

p.s. the extra mass will make it take longer to heat up and melt but not anything to annoying, and use lots of crisco on mellamine board.

[David Patchen]

Hey, good ideas, thanks! I like the idea of using some kind of castable or rammable to create a tray and support in the floor as it will catch spilled glass and prevent the furnace floor from getting demolished. (I already have a sand floor lining, but it's not very deep as the bottom element is pretty low). Casting something that will support the crucibles sounds great too. I like the idea of maybe jamming a few kiln posts into the casting around each crucible to keep the crucibles upright but not insulating them from the heat.

Hmmmm, will ponder further.

I tried googling to find distributors of castable refractory, but most of what I found were manufacturers with really frustrating websites (Why would you *not* highlight where I can buy some?!) Marketers, they are not.

Thanks again guys; if I can get my hands on some of the right castable I can get this done over the weekend and dip next week :)

[Dave Bross]

A few other thoughts...

Put them on individual squares of kiln shelf with some glass sprinkled between the kiln shelf and the pot. As soon as things heat up you get a super stable pot. I do this with those same pots for quickie color in the glory. They stay in place nicely and are easily exchanged as a unit. Put sand or grog under them for easy release.

or...

Wire them together...as in push them all together and wrap a bit of wire around them. I like the A1 wire better than nichrome but it's maybe a bit expensive for this.

[Ken Peterson]

maybe cast, then lay sand in the casting, then pop the crucible in. that way you can get them in and out easily.

[Hugh Jenkins]

Last I knew North American (RHI) had an outlet in Richmond 510-236-7415 and Western Industrial Ceramics in Hayward 510-782-2087.

[Richard Huntrods]

Don't know about shipping to Calif., or whether there is an outlet in the US, but I bought my rammable from Inproheat in Vancouver BC. They also carry a full range of refractory products including cement, castable and brick. Prices were very reasonable and shipping was not bad either.

Again, I don't know anything about shipping to the US from here.

Cheers,

-Richard

[Jim Wiltschko]

Hey Dave - Hugh's right about RHI. Take I-80 east to Pinole then the Richmond Parkway to Collins Ave. There's also Pyro Materials - love the name - in Oakland.

http://www.hwr.com

http://www.pyromineralsinc.com/

[Scott Hegan]

The guy at Harbison Walker in richmond is Dick Fox (510) 236-7415. Sometimes the products I need are at the Pico Rivera warehouse and they ups whatever I need directly to me, but you could probably save on some shipping by having them send it to richmond and pick it up. I have talked to rosie in pico rivera 562-942-2151 and she is nice. BTW they used to print the refractory handbook. I have found it to be one of the most useful freebees ever. Those crucibles are also fine for melting bronze.