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Mirror Making-Material
From Stathis Kafalis Copyright © 2019

Material order

I can supply borosilicate blanks in the standard sizes ex stock and can get other sizes in approx. 4-7 weeks delivery time. If you are interested, please contact me at the above e-mail address or call at +49 / 89 / 62 42 01 71.

The blanks are from Schott borosilicate glass, which has the same thermal and mechanical properties like Pyrex or Duran. The material is homogeneous, free of visible bubbles and free of internal stress or stain (as seen in the polarizer test). The blanks are cut from large sheets, they are considerably flat on both sides and come with a ground edge.

Countless fine mirrors have been made with them for decades. See examples in our mirror making workshop in Munich or in the Astrotreff Forum.

Prices including 19% VAT are as follows:

Borosilicate Glass Blanks:

Diameter Thickness Weight Price Euro Delivery
Status: 09. Apr. 2019
4,5" = 115 mm 15 mm 0,35 kg 18,- € Stock
5" = 130 mm 15 mm 0,44 kg 21,- € Stock
6" = 155 mm 15 mm 0,65 kg 28,- € On Request
 6" = 155 mm 21 mm 0,89 kg 38,- € Stock
7" = 180 mm 21 mm 1,20 kg 48,- € Stock
8" = 205 mm 18 mm 1,34 kg 59,- € Stock
 8" = 205 mm 21 mm 1,56 kg 60,- € Stock
 8" = 205 mm 25 mm 1,86 kg 65,- € Stock
9,4" = 240 mm 18 mm 1,83 kg 74,- € Stock
10" = 255 mm 21 mm 2,40 kg 88,-€ Stock
10" = 255 mm 25 mm 2,87 kg 96,- € Stock
10,6" = 270 mm 25 mm 3,22 kg 105,- € Stock
~12" = 300 mm 25 mm 4,11 kg 132,- € Stock
13" = 330 mm 25 mm 4,81 kg 156,- € Stock
13,5" = 345 mm 25 mm 5,45 kg 175,- € Stock
14" = 355 mm 25 mm 5,77 kg 185,- € Stock
~16" = 400 mm 25 mm 7,08 kg 235,- € Stock
18" = 460 mm 25 mm 9,35 kg 295,- € Stock
20" = 500 mm 25 mm 11,04 kg 360,- € On Request
Bigger or other sizes: on request

Sizes of 400 mm and up require some experience in mirror making

On request I can grind the backside flat up to grit 320 for 10,- to 30,- Euro, according to effort (recommended for 255 mm and larger)

Thicker Borosilicate Glass Blanks:
Available in the thicknesses 31,5 / 34,5 / 41,3 / 47,6... (up to 57,2 mm). Ideally suited for larger diameter mirrors. Same thermal and mechanical properties like the thinner material. Please ask for a quote and delivery time.

Grinding and polishing Material:
Grinding and polishing compounds I have nearly always in stock. A complete material set includes silicon carbide grit #80, #180, #320, Aluminum oxyde with specific flat grit shape and tight size distribution Microgrit WCA 25my, 15my, 9my, 5 my, 3 my, polishing powder CER-SKX (a very fine and pure cerium oxide) and optical pitch of 28° hardness. The grit K80 for rough grinding is in any case sufficient for f/5 or slower, the amounts on the finer grits, pitch and ceroxid are very generous, to handle even several setbacks. Everything is packed in double plastic bags to prevent cross contamination. Prices including VAT:

Material-Set Weight Price Euro
 4,5+5" 0,75 kg (contains 0,25 kg K80) 22,- €
 6" 1,2 kg (contains 0,35 kg K80) 27,- €
 8" 1,9 kg (contains 0,7 kg K80) 35,- €
10" 3,2 kg (contains 1,4 kg K80) 48,-€
12-14" 4,1 kg (contains 1,8 kg K80) 60,-€
Other quantities I can put together on request.
Grindstones to bevel the edge I supply for 5,- Euro (available at hardware stores as well)

Shipping cost see DHL and add 19% VAT or Hermes, or just ask me

The grinding and polishing tool is not included in the set. You will need to make this yourself or just order 2 blanks (which is still affordable at least for the smaller sizes). Tips on how to make your own tool see at tips and tricks (German text).

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