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Old 11-03-2018, 06:16 AM
Curtis Dionne Curtis Dionne is offline
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That's very interesting Michael. It seems like a
immense amount of wood and I have heard stories of deforestation around certain glass industries. I use a lot but I feel that it's very sustainable at this level.
I think with wood, it requires a certain number of BTU to effectively incinerate the fuel in addition to the BTU that is needed to melt the glass. The charge and cook process is a bit long, but its partly because I require sleep and so the firing schedule works out nicely over 2 days. I previously used 2 90 pound pots. One I charge with aste cullet and make blue. The other clear batch. I could charge over night and cook the next day only losing one day of blowing. Those were long nights and most important considering I will drain the clear in 2.5 days of blowing. I now have installed a 300 pound pot with three color pots. Its roughly 400 pounds of glass. I now get 7 or 8 days of blowing out of a cook, after which, 2 days of charging and cooking is a kind of welcome break. You see, when I come out in the morning the furnace is usually at about 975, like clock work, with a very hot fire box. The first couple 50cm sticks that I throw in see a 100 degree increase very fast. It then takes me several hours to increase to 1200, which is my preferred charging temp. I then continue to charge 50 pounds every hour and a half or 2 hours. So you can see that day one is pretty much spent. At this time, if I had a night drunk, the glass could be cooked over night. But i hate to take the idk of seedy glass. So instead i close up and sleep. In the morning I'm back down to 975 and spend the day putting around the shop and climbing to 1250. The furnace very easily goes to 1150 by or 10 in the morning which is when I usually start go blow. But this next 100 degrees I must work for. And i often dont hit 1250 until 2 or 3 in the afternoon. Then I hold until bedtime and squeeze again over night. This process ensures great glass and kind of gives my elbows a couple days off.
The furnace
So the entire furnace from floor to chimney is laid in hard 3000F brick. The arches are made from tapered bricks. There is a low arch that comes off the side wall to form the fire box. The wall then continues straight up to form the canter arch of the above chamber. The top of the fire box arch is filled in with hard castable to create a slightly sloping floor above the fire box. This is where the crucibles sit. I then drilled 2 3inch holes straight down into the fire box. These holes funnel the woodgas up into the top chamber, similar to a long venturi flame. These holes are over one side of the chamber. On the opposite side, a few inches below the rim of the pots, is the exhaust. So some of the fire flows directly across to the ventflowing by the sides of the pots like a river. Much of the gas, particularly during peak gasification, shoots straight up and rolls all the way around the long canter crown. So on the exhaust side the fire actually flows down. It creates ike a cyclone. I like to think the canter arch kind of focuses the heat back down at the pots like a lense. The hard brick is then covered completely with 4 inches of soft brick and one inch fiber board. Another 6 inches of fiber on the crown. Then the entire thing is covered in a 4 inch concrete and stone "veneer". every place possible between the veneer and the hearth is then stuffed with fibre and in some places as much as 16 inches of rock wool. Its seems to be very well insulated.
Yes, the build ended up a bit taller for some reason than it looked on paper. The side in the picture is the fire box side so there is not much that can be done. I built a small concrete step in case I need it as the pot gets low. But I find it is very comfortable to gather from when you get used to it. I find my back issues have subsided since I'm no longer crouching forward to see in as I gather. On the other side the floor slopes up then there is a small step up onto an elevated concrete pad. This is they side where I have the 13 inch glory hole door.
Still my yoke is at breast height. This I did find uncomfortable at first, but it has grew on me. And again I find it much better on the back because I can stand up straight and see all the way to the back of the furnace.
On the inside of the furnace there is about 17 inches of space above the pots plus the 26 inches wide and 40 inches deep. So there is a lot of space in there to keep hot and it is great for flashing long, super long pieces. I think this works well with the long flames of wood.
Air is controlled by a chimney damper brick at the base of the chimney and accessed by the chimney ash clean out. Also by controlling the amount of air that can come in under the grate through the firebox ash clean out.
By my calculation that I made before building the furnace, based on an estimated 250,000 BTU per hour burner, I would need to burn between 25 and 50 pounds of wood per hour at 7000 BTU per pound of wood. There's an estimated 25million BTU in a cord of yellow birch. So, on paper, it works out that at max output I will burn a cord every 4 days. Fortunately for me it's about half that!
I love my furnace, I love making glass over a wood fire.
I wouldn't change it. I think I'll get many more years use out of this one.
Any more questions?
Another thing to keep in mind is that my efficiency could be increased with more dry wood. It's hard to get ahead and all my fuel is stored outdoors currently.
Another bonus is that any overflows or leaky pots and the glass flows into the fire box and can be cleaned out easily from the ash cleanout

Just a quick edit here, I'd like to mention about how I came to this solution. In the last 15 years Canadian safety association has implemented extreme liability rules for any new gas appliances. As I spent most of my life as a labourer, I just dont and certainly didn't have the money to comply. It can be 10 grand just to get inspected, plus you need a technician to install any gas parts. Because of my rural setting I dont have access to 3 phase power either. An electric furnace would still leave me in the same CSA battle to build and install a simple gloryhole.
It can be very expensive and drawn out to get CSA approved for any gas equipment here now. When I apprenticed with Vargas we didn't have those problems because they were kind of grandfathered in. Burning wood in Canada waives liability issues and is tax free. This left me with a 20,000 budget for the build. And it worked out very nicely

Last edited by Curtis Dionne; 11-03-2018 at 07:41 AM.
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  #27  
Old 11-03-2018, 09:57 AM
Curtis Dionne Curtis Dionne is offline
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I appreciate your input on this David. I would like to share my thoughts. The furnace I learned on had gas and a blower. It had a small hole on top for a chimney. You could gauge the burn by how much flame came out that hole. And adjust it by the sound to get your mix. Much later I saw the studio of late and great Jon Sawyer of NB Canada. He ran venturies with a small 18 inch chimney. I believe it took him 2 days to charge and cook a batch. Much like the venturi, the wood furnace is flowing, creating a negative pressure atmosphere. It is this natural motion that supplies air to the fuel in balance as well as exhausts excessive heat and all batch fumes up the chimney and outside while promoting a complete and clean burn. This serves to give me the best possible air quality in my studio. If I were to add a blower it would only make sense to make it an exhaust fan located in the chimney. But the truth is that works fine without. The cook could be shortened but the 2 days gives me the best glass and sleep. it is also a welcome 2 days off blowing after the 8 day stretch on
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Old 11-03-2018, 10:02 AM
Eben Horton Eben Horton is offline
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Curtis, do you anneal with flue heat? Seems to me that would be where you could find a lot of savings.
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Old 11-03-2018, 10:56 AM
Curtis Dionne Curtis Dionne is offline
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Quote:
Originally Posted by Eben Horton View Post
Curtis, do you anneal with flue heat? Seems to me that would be where you could find a lot of savings.
Originally I did expirament with that Eben. My results were a bit unpredictable. I do love my electric sneakers. I considered more of a garage off the flue. But it just works so nice as a stand alone. Though, a steam boiler is not out of the question.
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Old 11-03-2018, 01:42 PM
Eben Horton Eben Horton is offline
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A friend who no longer makes glass built two annealera off of his flu. Imagine the flue splitting like a Y. Beneath each annealer was a damper he could slide like a gate valve. The heat entered the annealer and heated up a 2 inch slab of castable that formed a floating floor. There was an opening at the top with another damper. He would alternate each annealer every other day. On days he charged he would in cap the flue that popped out of the middle of the Y. It worked great. The castable was mizzou and would act as a heat sink and provide a minimum of 12 hours turndown. He was super proud of it. The flue was built out of fiber board and stainless mesh that was wrapped in Portland cement.
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Old 11-03-2018, 06:59 PM
Travis Frink Travis Frink is offline
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Quote:
Originally Posted by Eben Horton View Post
A friend who no longer makes glass built two annealera off of his flu. Imagine the flue splitting like a Y. Beneath each annealer was a damper he could slide like a gate valve. The heat entered the annealer and heated up a 2 inch slab of castable that formed a floating floor. There was an opening at the top with another damper. He would alternate each annealer every other day. On days he charged he would in cap the flue that popped out of the middle of the Y. It worked great. The castable was mizzou and would act as a heat sink and provide a minimum of 12 hours turndown. He was super proud of it. The flue was built out of fiber board and stainless mesh that was wrapped in Portland cement.
A friend had something much lik that which seemed to work great. He has since downsized to a one man show and has one with only one annealer. The two sided annealer allowed for annealing larger/thicker work than I see as reasonable now. Things did not always cut so cleanly out of that annealer indicating they are not properly annealed?

Another friend has a single annealer off the side of his flue with elements in it to assist and control finitely. He anneales thick and complex work which later cuts very cleanly. Initially this was also heated with flue heat alone but things broke and the electric assist solved that problem. However he usually can't take work out of the annealer til noon so mornings are usually spent cold working, packing, prepping cane/murrine etc.

Putting work into an annealer that is shoulder height is not nearly as hot as ones lower down. An uninsulated long leather glove is plenty when putting work in with tongs. And the leather never gets hot unless you're in there much longer than you should be.
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  #32  
Old 11-03-2018, 07:02 PM
Travis Frink Travis Frink is offline
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Curtis, that really is a great way to blow glass. I wish it worked with softwood as there is a significant need to find a way to reuse the cedar and cypress trees thinned from the forrests everywhere around my area.
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  #33  
Old 11-03-2018, 07:09 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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So I realize that this works fo you
But just as a discussion
There was talk of blowers, that would be real unnecessary, a 6-7 meter chimney would create all the draft you'd need to melt iron ore in your furnace :-)
I dont see a chimney in that youtube film
What about a motor controlled damper in the flue, governed by a temp controller, to control the temperature?
The moisture content of the wood is all important, every fall I have 32+ cords super dry split wood inside a storage building of mine ( together with tons of obsolete glass equipment, a1955 TED 20 Massey Ferguson tractor , a wood boat project and more)
The wood is split and put in in April and a blower pull air 200 meters in a zig zag pattern under the black corrugated sheet metal roof and blows it across the wood all summer. The record is 54 C but even on a cloudy day the temp-is 20C above outside temperature
I burn a bit of this on cold days in a cast iron stove in the house,but mostly I keep it as insurance against the big sun flare, or Trump nuking Key West or something
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Old 11-03-2018, 07:43 PM
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Pete VanderLaan Pete VanderLaan is offline
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Indeed, I think that doing a kiln dryer for the wood makes a bit more sense to me. Anneal with electricity and be accurate.
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  #35  
Old 11-03-2018, 08:29 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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Yes annealing should be electric, its a very easy solution to a complicated problem, and low cost.
Forget flue solutions
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  #36  
Old 11-04-2018, 02:30 AM
Curtis Dionne Curtis Dionne is offline
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The flue annealed was terribly inaccurate and added stress to my day and my glass. I do have a chimney about 5 meters high to clear the roof peak. The furnace works great as a stand alone unit. I dont have to worry about it getting too hot and the air intake can easily be adjusted as needed. I just slide a brick around a bit with my foot If needed.

Solar wood drying shed sounds great. Putting that on my to do list
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