Clamshell Oven

[Joe Deanda]

I have recently been doing lots of murrini and cane pick ups using a pastorelli, glory hole . I have a old but new element from a 200 lb denver furnace and also the contol box from that long gone furnace. Im thinking about building an open bottom unit with a 1/2'' steel plate with a fan blowing on the bottom of the plate. Build a Lid with metal on the outside and frax for the insulation and then castolite 30 for the hot face. Mount the element in the lid with a mullite tube inside each coil for anti-sag mounting. Hinges on the back to get the lid up and out of the way.
The reason I like this concept is so that the pieces will remain stationary while being heated and not get moved around while heating. By blowing on the bottom of the steel plate it shouldnt get so hot as to make the pieces stick while getting hot enough on the top to pick up well. Anyone ever seen anything like this or am I a mad scientist. Its not like im working on an anti-gravity machine or anything. Thoughts and suggestions will all be considered and appericated.
JBlo :beret:

[Brody Shaw]

yup, but that element might be overkill...

but what you propose will work...

[Steve Stadelman]

I love the whole idea, lots of people do that now. I would just substitute dense fiber board or marinite for the cast-o-lite.

It can actually be cast-o-heavy if you get much of it around.

[Jordan Kube]

A clam shell with elements on the top will work great. I wouldn't make it too complicated.

[Brent Hickenbotham]

which direction do you propose on blowing the fan, i only ask to keep you from getting a blast of frax in the face every time you open the lid. you might try some welded heat dissipating baffles on the bottom of the plate. i.e. 3/4" flat stock welded in rows on its sides with fan blowing parallel.:blow:

oh by the way its a great idea.

[David Patchen]

I think this sounds great. When I was in Italy, the master I visited had a clamshell pickup oven with top-mounted elements in quartz tubes. They didn't have an open bottom, but they definitely had their heat and timing nailed. Always gently fused, never any sticking on steel plates. Steel, bah...traditionalists.

I thought about making something like this at one point, but my assistants are now pretty damn good at not overheating my pickups, which I do on preheated kiln shelf which are transfered to the hole. Yelling at them when they overheated pickups in the past seems to have had a nice and effective deterrent effect.

I don't think you need the fan. I think if you're careful with your heat the steel acts as it's own heat sink. Think about the glory--it's heating the plate from all sides and if you're good you don't get sticking, so why should a top-heat kiln? BTW, I haven't used steel in years and don't see any reason ever use it for plates. I'd get some kiln shelf and some wash. Way better.

I'd stay away from any kiln material that will potentially get your pickups dusty (hot frax?). Nothing sucks more than having an inclusion that's part of your equipment falling onto your pickup.

I'd also want the elements running the 'long way" and pretty closely spaced for even heat. It would suck to have hot spots in a clamshell.

If you put this thing together please post photos. I may do something similar in the future.

[Todd Anderson]

Wale Apparatus has a decent clamshell like the one Dave describes - this should be the link http://www.waleapparatus.com/details/40_1810.asp

[Joe Deanda]

thanks for the input everyone.

Steve good idea trying to make the top lighter.

Brent I planned on blowing up from the bottom at the bottom of the steel plate.

David you have some good points with using a kiln shelf and some experienced assistants. My current assistant is still fairly green and lots of the time we work alone. Were in a theme park setting and doing demos for 9 months out of the year. I really didnt have plans for any exposed frax. The frax would have been behind the cast - o- heavy ? Thanks for the ideas that will modify the design. The next step is to get permission and funding from the maintence and safety people at the park. Sometimes thats the hardest part, getting approval from people that know way less than we do. :headbang: David your work is amazing ! thanks again Joe