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Mirror Making-Material
From Stathis Kafalis Copyright © 2020

Corona News: My business is well and running. DHL parcel service is restricted to some areas of Europe and overseas only. For details see DHL Corona Information or just ask me.

I 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 transparent, 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.

Borosilicate Glass Blank prices including 19% VAT

Diameter Thickness Weight Price Euro Delivery
Status: 25. May 2020
4,5" = 115 mm 15 mm 0,35 kg 21,- € Stock
5" = 130 mm 15 mm 0,44 kg 26,- € Stock
6" = 155 mm 15 mm 0,65 kg 33,- € Stock
 6" = 155 mm 21 mm 0,89 kg 44,- € Stock
7" = 180 mm 21 mm 1,20 kg 56,- € On Request
8" = 205 mm 18 mm 1,34 kg 67,- € Stock
 8" = 205 mm 21 mm 1,56 kg 70,- € Stock
 8" = 205 mm 25 mm 1,86 kg 75,- € Stock
9,4" = 240 mm 18 mm 1,83 kg 82,- € Stock
10" = 255 mm 21 mm 2,40 kg 95,- € Stock
10" = 255 mm 25 mm 2,87 kg 108,- € Stock
10,6" = 270 mm 25 mm 3,22 kg 119,- € Stock
~12" = 300 mm 25 mm 4,11 kg 147,- € Stock
13" = 330 mm 25 mm 4,81 kg 175,- € On Request
14" = 355 mm 25 mm 5,77 kg 200,- € On Request
~16" = 400 mm 25 mm 7,08 kg 250,- € On Request
18" = 460 mm 25 mm 9,35 kg 325,- € Stock
20" = 500 mm 25 mm 11,04 kg 390,- € On Request
Bigger or other sizes in various thicknesses from 5 to 25 mm available: 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.

Grinding and polishing Material prices including 19% VAT:

Material-Set Weight Price Euro
 4,5+5" 0,75 kg (contains 0,25 kg K80) 23,- €
 6" 1,2 kg (contains 0,35 kg K80) 28,- €
 8" 1,9 kg (contains 0,7 kg K80) 37,- €
10" 3,2 kg (contains 1,4 kg K80) 52,-€
12-14" 4,1 kg (contains 1,8 kg K80) 63,-€

Other quantities I can put together on request.

I supply Grindstones to bevel the edge 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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