NJBA Gas Forge Workshop April 2004

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Gas Forge Workshop
By Jeff Morelli
On April 3rd NJBA members got together to build 21 single burner gas forges.The plan was to roll 12"x12"x12" cylinders, line them with 2" of Kaowoll, install a supported kiln shelf on the bottom, an insulated rear door and a burner assembled from new parts including an adjustable regulator. To keep costs members would have to provide their own fire brick for the fronts.

At 9 AM we split into teams for rolling, welding, burner assembly, cutting and fitting the Kaowoll, sheet metal work, leak testing the hoses, etc. Most fabrication was done by lunch break since many special parts had been made in the previous few weeks.

By 2:00 the first forge was being tested by Marshall who gave a lesson on how to light the forge adjust test the flame. Twelve forges were sold and taken home by NJBA members, who were eagerly awaiting the following weekend to light them - the kiln shelves needed to cure another week and then be heated slowly.

Special thanks go to Marshal Bienstock for use of his shop, John Chobrda for buying the Kaowool and burner parts, Bruce Freeman for casting the kiln shelves, Dave Macauley and Tom Eden for pre-fab work, Bruce Hayes, Larry Brown, Mike Erdie, John Chobrda and Marshal for welding. If any NJBA members are interested in buying one of these "Must Have" forges, give Marshal Bienstock (directors list page 2)a call, they are a bargain at $200 apiece for members.

Casting "Kiln Shelves" for Gas Forges
Bruce Freeman
Forms were made using 3/4" plywood, covered with plastic (garbage bags cut open). (It would have been better to have made more of an effort to stretch this plastic tight, as wrinkles cast into the shelves.) These were divided by means of nominally 1x2 (3/4" x 1.5") furring strips. Since the shelves were to be 7" wide by 12" long, 12" lengths of furring strips were placed between, and perpendicular to, longer pieces to form a grid. The furring strips were mounted to the plywood with 1 5/8" coarse wallboard screws.

The casting material was a (non-insulating) castable refractory cement, rated to 2800 F. Two 50-lb bags (about $34 total) were needed to make 21 shelves. The shelves were reinforced with 1/2" 304 SS wire clote (of 1/16" wire - slightly smaller wire would have probably sufficed), which was purchased in 12" x 24" pieces from McMaster-Carr (for about $13 ea). Each was cut using a heavy shear into ~6.5" x 11.5" pieces.

The refractory cement was mixed as per instructions, an entire bag at a time. Each shelf form was filled about halfway, then a piece of the wire mesh was inserted firmly. The form was then filled to the thickness of the form (3/4") or sometimes slightly thicker.

After setting two days, the wallboard screws were removed and the cast shelves broken apart from the furring strips. (The cement adhered somewhat to the furring strips, and had to be broken away gingerly. A wax or other mold release would have helped.)

These shelves need to be cured slowly before being brought up to a red heat.

Shelf Legs for Gas Forges
Bruce Freeman
Ice cube trays were used as molds for casting legs from refractory cement. (Egg cartons might have worked.) In retrospect, a mold-release should have been used, as the cement tends to adhere even to plastic. Insulating castable refractory cement was prepared as per instructions and troweled into the trays. The trays were covered with cardboard and left to set for two days. Unfortunately, when the trays were examined two days later, the cement was still wet, with no apparent setting whatever. When it had dried, it merely crumbled. This fiasco was apparently due to the fact that the bag had been broached in 1998. It had not been waterproofed afterwards and, apparently, had picked up water in the intervening years. This was unfortunate, because ice-cube sized lumps of refractory would have been perfect legs for the shelves, six to eight per shelf.

Instead, ~1" thick slabs were cut from noninsulating fire bricks using a chop saw with masonary blade. (This was a messy, dusty process, requiring goggles and dust mask, however, attempts to cleave these bricks with a chisel were not successful.) These pieces of brick apparently function acceptably as legs.

(Note: in the April, 1998, gas forge workshop, bottoms were cast in place in the forges using insulating refractory cement. That procedure was effective, but inconvenient.)

Click "HERE" to go to a page about gas forge use and safety.