View Full Version : New Person

Mike Spencer
04-13-2012, 08:23 AM
Hello.. I'm new and my name is Mike..

I have some questions about aKiln I just bought, It's a Duncan ES1020-2.. I haven't tried it out yet.. and need to find out a few things .. 1) the top/lid is a spongy white maiterial.. it seems great on the inside but on the outside top is a hard layer that is coming off in places.. they guy I bought it from says that is normal.. but I would like to repair it ..somehow.. the rest on the Kiln seems great the firebrick on the walls looks new or really great.. and there is cracks across the bottom.. I am new at this .. never had or used a kiln before.. and would like to test it out... any suggestions would be welcome any place I can read up on it would also be great.. also can someone tell about when this kiln was made.. and is it a good one

Regards.. Mike

Rosanna Gusler
04-13-2012, 09:52 AM
hi mike. are you planning on using the kiln to fuse glass or to melt a pot of molten glass for glass blowing? if you are planning to fuse glass www.warmglass.com bulletin board and the tutorial there might be a better place for you to start. this board is mostly glass blowers. great information is to be had here but fusers find warm glass more usefull. welcome to the addiction in any case. rosanna

Mike Spencer
04-13-2012, 10:13 AM
actually I want to try to fuse 6-20 inch 1/4 to 1/2 inch glass circles into Telescope mirror blanks..I want to use 3-6 layers of the circles. I have ordered parts to create a digital temp. controller.. to better gauge and control the temp. of the kiln.. anyone done this...


Ted Trower
04-13-2012, 12:56 PM
I hope you are planning a first surface mirror?

Mike Spencer
04-13-2012, 01:32 PM
That is correct. you have to grind a first surface spherical mirror.. then parabolize it... then have a aluminum type coating on it...pyrex isn't being made by corning anymore and telescope mirror making are looking towards plate glass..


Tom Clifton
04-13-2012, 03:34 PM
pyrex isn't being made by corning anymore and telescope mirror making are looking towards plate glass..

I believe all plate glass is soft glass (soda/lime) The current "pyrex" made by World Kitchens is tempered soda lime glass. (There was a recent thread here about that...)

If you want a low expansion glass you can use borosilicate glass. You should be able to make circular molds and cast your own. With your kiln you can anneal them. From a mechanical/thermal issue I don't know how critical it is that the two surfaces be absolutely parallel, but I should think that would the same issue if you fuse plate glass as well.

Not being a home-brew telescope guy I have to ask if there are other forums on scope making where casting your own has been discussed?

Steve Stadelman
04-13-2012, 07:25 PM
I did this way back in the day. I ended up casting some 24" by 4" thick Pyrex blanks. What a waste of time.

Mike Spencer
04-14-2012, 07:46 AM
Thanks for the replies.. I'm not really looking for info for making mirror blanks..( I have some info on that already) But on the Kiln I have and pointers in using it.. I have never had or used one before.. I just brought up the Glass fusing so you would know what I would be using it for.. Again its a Duncan model ES-1020-2 240v it about 2o some inches across and about 27" deep..it has a lt-3k sitter..the fire bricks look fairly new.. the lid/bottom is made of some white fiber material ..the lid on the outside has a harder coat that flaking off.. I wanted to know what that was and how would I go about recoating it...


Steve Stadelman
04-14-2012, 09:58 AM
Post some pics. It sounds as if it might be a rigidized fiber with a mortar wash coat.

Mike Spencer
04-15-2012, 07:28 AM
I'll try to get pictures posted... I cleaned out the kiln and wired a dryer plug to it.. and plugged it in the dryer outlet.. both are 30a ... question.. setting it on low the Infinite switch clicks on and off every few min. switch it to med. and it still switches on and off but longer inbetween.. and on high it stays on.. is this normal.. also when the switch is on I hear a humming or low buzzing .. is this also normal... again.. i am totally new at this...

regards.. mike

Rosanna Gusler
04-15-2012, 08:42 AM
yep all of that is normal. kilns are generally underinsulated. they get hot. that means nothing flammible next to, above, or below the kiln. rosanna

Mike Spencer
04-15-2012, 09:59 AM
Great Thanks.. I am relieved.. I was worried something was wrong...


Henry Halem
04-15-2012, 12:04 PM
Just so you know, Duncan is no longer in business. Their assets were purchased by Paragon Kilns. You can get parts for Duncan through them.

Scott Novota
04-16-2012, 01:11 PM

At one time I think I had the same kiln as you did. That top will continue to fall apart over time of course.

I ended up just making a new top out of 2 sheet of 2 inch fiber board laid on top of each other cut to the time of the lid. I braced them with lenths of 1/16 steel and ran a bolt though them to lengths accross the top to give it some strength. It is far as I know still being used to this day as a back up annealer at a local public shop I donated it to years ago without any other fixes. Hell I think it is down to one element out of 8 and still being used if it is still in the condition I saw it last.

Joe Pfeifer
04-19-2012, 11:54 AM
I know that Dan Cummings from Spectrum Studios in Salt Lake City built a special kiln to make a very large borosilicate lens blank for someone in europe. https://p.secure.hostingprod.com/@www.artistsofutah.org/15bytes/10mar/images/ssl/13.jpg

They may be able to help.

Victor Chiarizia
04-20-2012, 07:50 AM
i've done pyrex mirror casting before and can tell you it's a very exacting chore. any mistake or stress will come out in the figuring stage of grinding. my 16" cell mirror had astigmatism but it was still an impressive looking mirror and won me an award at stellafane for innovation. if i did it again i'd use ohara E6 glass.....i think ~ $50 a lb. but lower melt and better flow.
theres a short vid on my website i think of the scope and mirror from 10 years ago.

Scott Novota
04-20-2012, 10:21 AM
I am always surprised by the depth of experience here.

Pete VanderLaan
04-21-2012, 03:48 AM
The Tuscon project dealt with that by using a honeycomb structure for the castings so the astigmatism was really mimimal. They were casting 36 foot mirrors in that big revolving kiln. That was the highlight of the Tuscon conference for me.