KILN/FURNACE

How We Got Here from There...

THEN

Twenty five or more years ago, a friend loaned me a copy of "Lindsay Publications Catalog". I was taken with some "how to books" by Dave Gingerly, describing a charcoal fired blast furnace built in a five gallon bucket. This little furnace would melt one quart of aluminum.  It was the starting place for making an entire machine shop, with each machine being constructed of parts which could be cast with one quart of aluminum or less. I bought his book and built the furnace.

Upon completion, my sons and I collected soda cans, and using green sand molds, we cast belt buckles. It was great fun, but we eventually lost interest and stored the furnace.

RECENTLY

My wife and I saw some "slumped" glass bottles, and she being a talented painter and crafter, thought this would be an interesting subject for decorating. We bought a small electric kiln and successfully slumped  some bottles, but it was only large enough for soda and beer sized bottles. The more colorful and interestingly shaped wine and liquor bottles were too big.

Hmm... if we added a larger diameter extension above the small kiln it would allow us to slump the bigger bottles. Problem was I'd misplaced Dave Gingerly's book and couldn't remember the formula for the refractory lining.  I began searching the Internet looking for formulas. During the search I came across a "Lost Foam" site. Being curious (I knew about lost wax but hadn't heard of lost foam), I went in and explored. This site directed me to another "Lost Foam Primer" where I found enough information to make me believe it would be possible to cast small statues. Suddenly I was chasing rabbits!

I'd started out to enlarge the small electric kiln for slumping bottles and now here I was thinking of casting aluminum (distracting dang Internet). I built the kiln extension using a section of a fifty-five gallon barrel and then altered an old angle iron saw table to support the barrel extension above the kiln. Armed with a refractory formula adapted from several found on the Internet, the kiln extension was soon ready to try.

OOPS: The little electric kiln couldn't handle the additional space...

CHARCOAL TO PROPANE: Meanwhile collecting more information from various web sites, I decided to convert the old charcoal furnace to use a self-aspirated propane burner. It worked well but used over half the volume of a 20 lb. propane tank to melt one quart of aluminum. Not exactly economical. (This did allow me to try a lost foam experiment, which was successful enough to spur me on.)

PROPANE TO WASTE OIL: Attempting to reduce operating costs I tried several designs of waste oil burners. Then discovered Colin Peck's web site. His book was given to me as a birthday present. I devoured it and was off and running. Built following his instructions, I soon had an operating waste oil burner.

BURNER PROBLEM: After adapting the Gingerly five gallon furnace to use the new burner, I found some problems which kept me from achieving melts that should be possible with this combination.

SOLUTION: Colin encourages contacting him with problems, which I did. Over time, e-mailing, testing, emailing, testing, etc., he solved the problem. Basically the burner needed to be reduced for my small furnace.

IDEA: Now able to melt aluminum, my thoughts returned to the fifty-five gallon barrel kiln. The Gingerly five-gallon furnace with the Peck waste oil burner was close to the physical size of the ineffectual electric kiln. So why not exchange the kiln for the five-gallon oil fired furnace?

EXHAUST PROBLEM: The little furnace exhausted out its lid, which seemed a problem at the time. Wouldn't the flame and exhaust entering the fifty-five gallon kiln section somehow damage the glass?

SOLUTION: A tall new furnace lid with a side exhaust should replace the old lid. So, I decided to cast the side exhaust lid around a ten inch diameter stainless steel stock pot ten inches deep. The bottom of the upside down pot would extend into the kiln. This should radiate and heat the kiln enough to slump glass while exhausting out the side without damaging the glass. A humdinger idea..... don't you think?

OVERKILL: Because of the ferocious heat possible with Colin Peck's burner (designed to melt iron you know!) within fifteen to twenty minutes I'd melted the bottom out of the stainless steel pot! (I've learned to control it now.)

BACK TO THE DRAWING BOARD: I now had a fifty-five gallon kiln seventeen inches inside diameter, resting on a side exhaust lid ten inches inside diameter, resting on a six-inch inside diameter furnace. While at the above mentioned drawing board, it came to me, why not make a ten-inch inside diameter furnace bottom for the side exhaust lid? Then it would be a ten-inch inside diameter thirteen-inch deep furnace with a seventeen-inch inside diameter ten-inch deep kiln resting on it!

Wow! I could melt aluminum, then install a kiln shelf with bottles on it and slump while the kiln/ furnace was hot.

And here's how that works:

While the furnace is hot	Slumped Bottle	Decorated bottle

NEW PROBLEM: There was another problem going on all the while the above was progressing. The weather!! We had the third wettest spring and early summer here in the Ozarks ever! The whole apparatus needed to be under a roof somehow (rain/wind don't mix with foundry tests).

SOLUTION: I needed to replace Colin's external burner with an internal type so the open flame would be totally inside the furnace. Construct, test, modify, test, modify, etc.

Serendipity also played a part and finally, "Even a Blind Pig finds an acorn once in a while!" It's working!!! The internal type oil burner had finally evolved into its present working version.

TESTIMONIAL: I'm very satisfied with the kiln/furnace as it is now. It operates two feet inside my shop with a six foot long flue pipe to exhaust safely past the roof overhang. I can melt in spite of adverse weather. How cool is that?! (I mean hot!)

LARGE SCRAP: Because of the large diameter of the upper portion of the kiln/furnace, it allows reducing large pieces of aluminum scrap down to ingots that fit my crucibles. This was accomplished by constructing a funnel made of refractory, which rests inside the upper kiln section above the furnace. Large scraps placed on the funnel will melt and flow down into a waiting crucible, and then poured into ingot molds. The whole thing now can do the work of two furnaces!

CAPABILITY: Interestingly when gaining a new capability, new projects appear. For instance wanting to do lost foam casting, it became necessary to build a hot wire cutter for the foam.

HOT WIRE FOAM CUTTER

Back to the Internet again. I found enough information to form a loose plan, then adapted it to my collection of parts. The result is a homely looking but serviceable cutter. Built using scrap lumber, an old battery charger and a wall mount light dimmer, a heated stainless steel fishing leader does the cutting.

Foam cutter made from bits 'n pieces	Foam cutter at work

FOAM PATTERNS & MOLDS

The learning curve for cutting foam is pretty short. Patterns to guide the cutter ....somewhat loooonger. To use my foam casting pattern requires coating it in several layers of plaster, after runners and vents are attached. The plaster coated pattern is buried in dry sand for support. Pouring in the hot metal vaporizes the foam and fills the void left behind. Pretty cool! (I mean hot! Oh, you know what I mean!)

EPS foam pattern	Lost foam mold drying	Finished castings