Steel or Plastic 55 gallon drums are the current best 24 inches in diameter. Society of Greater Hartford's mirror class, which he leads. 
See First off, Pyrex cookware isn't
I just wanted to try it with this one to see how it looked. ask if they have any thick glass in the back room that they are willing to sell. Traditionally, a glass tool was used, but these are more expensive, and work slower. between the mirror and tool to grind the glass. Here is the Duncan kiln I got at a yard sale for only $95. temperature by a little bit. It measured 30 X 60 inches and weighed a ton. Only registered users can write reviews. Let the glass soak at 1700 for at least 10 minutes. The blank came out very round and didn't stick
Now that I have several blanks made, it is time to grind and polish one into a telescope mirror and test it out. This isn't the biggest blank I can make in the new kiln. 10 inches is absolutely the biggest blank I can make in my kiln. So I have the kiln at it's highest setting to get to 1700 as quickly as possible. is at least from the same lot. blanks sitting on top of it. kiln was now ready for firing. large trepanning saw and cut mirror blanks out of thick scrap glass. All Rights Reserved. turntable is more than adequate. will need to be chiseled off once it cools. 
deep scratches, you can be sure it is not tempered and can be cut. Once cleaned, I only handle them by the edges. clamped around the glass. The glass blanks have a lot of internal stress that needs to be relieved. A square wooden grinding It takes on the
The one part of the telescopes I have never made for myself is the mirror blank. This is important. I open the kiln with a long pole and wearing elbow length thermal gloves. I am in the process of making a better mold before doing any more 10 inch
your mirror to stabilize. Manufacturer of standard and custom optical instruments for food and medical industries. and distortion due to support in the telescope unless additional precautions are taken. bought before.
or as router work holders in home centers. before you finish assembly. This saves huge time in fabrication, and means that I can produce more mirrors with less work. It is amazing how much pressure an inch and a half of semi-liquid
I turn the kiln off and open the kiln for 15-20 seconds (or as long as I can
Don't waste your time with the tempered stuff. This is an operation that saves huge amounts of time and abrasives. it cool to room temperature naturally. See How to Make a Tile Tool. you. needed to constrain the glass and keep it in a disk shape. styrofoam. connected between these cleats in the diagonal pattern shown to form the "barrel". Usually I have the back of the blank "Blanchard ground" to a very flat surface. 
When storing grit, we always use a plastic bag in addition to the stiff container. glass to seep under it. Click the photo for a larger view. weighs 20 lbs, 10 oz. zip-closure food storage bag, inflated with air so that the bag does not rest on the lap's surface. I'm using Bullseye Kiln Paper. You can clamp this to a kitchen The idea is to keep them clean so that
needed. The blank is quite rough around the edges. heating the blanks back up to 900 degrees slowly so they don't break due to thermal shock. This is to prevent the hydrostatic pressure of
The insulating properties of the mold might also inhibit proper annealing. Ok, so this process isn't really quicker or easier than my friend's trepanning saw, However, my kiln is smaller and quieter than his saw, and
They have straight sides, parallel surfaces and virtually no bubbles. Then I turn off the kiln and let
I am working with the experts at the SPAC Mirror Lab on the fabrication and testing of this mirror. //-->, [Back to Mike's telescope workshop]
The extra weight is needed to prevent the mold from floating up and allowing the molten
If it has any chips or nicks in it, that's
about where to purchase these items. Here three 1/2 inch thick circles are stacked on the
Click the photo for a larger view. and to simply reduce the length of time the run takes. It is a fine-looking, near full-thickness, 10 inch diameter blank that I intend to grind and polish into a 1st class telescope mirror. UPDATE
The entire firing cycle took about 7 hours. I have experimented with various temperatures. Some people wrap their mirror in a clean cloth or towel, and store it in box. the entire kiln with hardly any room to spare. Working on the mirror for only a few hours, one day a week at the
I ruined a lot of glass, but I learned a lot. Nantong Jingsheng Optical Instrument Co., Ltd. How to souce products on Alibaba.com effectively? Website Last Modified July 30, 2022. Containers, Grinding Stands, and Miscellaneous 
The strips are held in place with tiny pieces of Scotch tape. This is the focus of all your work - you will turn this flat piece of glass into an accurate Your lap needs to be stored in a container that will not rest on the lap's surface (and deform it). into the soft bricks. This is one of my early blanks made of many thin layers. K-23 firebricks I used to make the 8 inch mold above. I have just completed my first 14.5 inch blank in my new kiln. with several wraps of stainless steel wire. charred by the heat (except me). The object sticking in from about 7:00 is the thermocouple
Since I perfected the above procedure though, there haven't been
Thomasnet Is A Registered Trademark Of Thomas Publishing More Glass!! will be tight. As before, the two halves of the mold will be held together
ITAR registered. The machine was huge, took forever to cut the glass, and finding thick enough
Grinding Tool: We recommend using a plaster and tile tool for grinding: The are inexpensive and easy may try that in the future. I made it by cutting 1/2 inch wide circular sections out of the same sort of soft,
But few use wooden barrels anymore. I've gotten quite good at cutting circles out of glass. Recently becoming popular is to use a disk of non-skid mat, sold as draw liners in supermarket or discount stores, glass tool, you will gain some of the speed advantage of a tile tool. Large billet sizes are custom manufactured as per requirement. really well.