It is of course, possible to make a furnace that costs very little to run, but the real question is....what comes out of the other end? If we go too far, we end up with seedy, unrefined glass that we have to sandblast to be able to sell. In my opinion, a furnace needs to be capable of delivering excellent quality glass, every day.
Perfect glass quality from the RGH1 (Bob)
So, if you want to make money out of glassmaking, the first question must be, "What scale are the products am I going to be making?" The second question is "How many products will I be making?"
There are two giants of furnace design in the UK. Many people argue over which is more efficient. Strangely, the answer is 'both of them'.
If you are a sole trader, perhaps working with a part time assistant, making batch production, but spending an equal amount of time on coldworking, design and paperwork, then Peter Howards extremely well insulated 150KG pot furnace would be perfect for you. The burner is small and efficient and the recuperator is so well designed that you can put your hand right over the flue, even when it's on high fire.
If you have a team of glassmakers working together every day, with staff to do the coldwork, then you can't go wrong with the best workhorse I've come across, Mike Tuffy's MRJ 150kg pot furnace. It has a poweful burner that can take the temperature to high fire like a rocket. It's not as insulated, but that means that after the overnight melt, it's sitting ready to be worked when the glassmakers come in early in the morning. (A well insulated furnace would take all morning to come down to working temperature).
Even though the MRJ looks more expensive to run on paper, it's possible to get more product out of it, which is just as efficient a business model.
My design for the RGH1 is the right business model for me at the moment. I designed it to be rugged and have spent less that £40 on maintenance on the furnace over the last 3 years. It was worked an average of 3 days a week for a year between 2011 and 2012 and has travelled to numerous sites for workshops, the most recent at the Plymouth College of Art event 'Field of kilns'. I've found that it can also be used like a micro furnace providing the pot is emptied, where we light it 1st thing in the morning, and work it 2 hrs later. We can even fill the pot up again right to the top and have usable glass within an hour. We got though about 50 kg at the last student workshop we ran at PCA, and often use a gathering ball to do sandcasting. At the end of the day, we just turn it off. This only gives seedy, unrefined glass of course, but costs about £15 per day on propane. (Much less on natural gas)
I'm delighted with the results and would like to thank Plymouth College of Art for their excellent support. I'll sign off with a few pics of the work that came out of the RGH1.....that's what it's about after all.
The first piece of refined glass that came from Bob 2 at the IFG last year. After many practical problems which caused a lot of inefficient burning, we got better glass quality than that from the furnace at the festival.
Upcycled glass. This is 50% recycled bottle glass altered so that it works as soft as lead crystal and can be decorated with any kugler colour. Cuts my cullet / batch costs by half.
Bob at the field of kilns, with small lehr over the gloryhole
Sandblasted bottle - all I can do with un-refined glass
38cm High vase, made in 2 parts and assembled using top loader. Refined glass quality, sells for £120. Costs on propane £45 (£30 natural Gas). Stock made easily in one day
Thanks to Plymouth College of Art