Will need to make one once I have the 14x17 back completed. Can anyone point me to a website or how to get started? Thank you.
You can try a 1/32" glass from your local hardware store and sodium hydroxide. Just brush it on, wait a few minutes and rinse off. It leaves a fine grain very smooth surface.
You can try a 1/32" glass from your local hardware store and sodium hydroxide. Just brush it on, wait a few minutes and rinse off. It leaves a fine grain very smooth surface.
I experimented with armour etch on some 4x5 glass. I could never get an even surface brushing it on but I did get a fairly usable glass by floating it, although I did get some around the edges on the clean side. I don't think it would be feasible with a glass that big.
You can try a 1/32" glass from your local hardware store and sodium hydroxide. Just brush it on, wait a few minutes and rinse off. It leaves a fine grain very smooth surface.
I've had good results using 600 grit emory on a random orbit sander, on 2mm Lucite sheet plastic, available from big box hardware stores in US. It's not glass, but it's also inexpensive and easy. And the results are pretty good.
I've also done the same with the 8.5"x11" plastic fresnel sheet magnifiers, available from Staple's office supply. The reverse side is flat, and takes the emory sanding pretty good. Then orient the sanded side toward the lens, and you have a GG with built-in fresnel.
~Joe
None of them give nearly as good results as using some fine powdered grit and using a glass block as a grinding blank.
I'm curious -- why does the block have to be glass?
Because the grits grind both surfaces, if the material's softer it'll get ground in preference to the glass if harder the ground particles from it will interfere with the grits ands it can scratch the glass being ground.
When grinding plastics glass tends to cause scratches very easily, so you grind with something similar.
Ian
No. If the material is softer, the abrasive will embed in it, forming a lap, grinding the harder material. It doesn't have to be a block of glass, a block of steel will work as well. One advantage of using a block of hard material is the fact that the abrasive will not embed, making it easier to attain a random pattern.
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