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#1 KI5CAW

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Posted 06 August 2022 - 11:33 AM

I'm toying with the idea of making a mirror: tried it in my youth but didn't have the patience for it. Back then the tool was another disk of glass. Today it seems like makers commonly use plaster tools faced with tile. But many of the questions on this forum deal with problems with plaster, tile, epoxy etc. So the question is, why did makers go over to tools made of something other than another simple disk of glass?



#2 dan chaffee

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Posted 06 August 2022 - 11:55 AM

I'm toying with the idea of making a mirror: tried it in my youth but didn't have the patience for it. Back then the tool was another disk of glass. Today it seems like makers commonly use plaster tools faced with tile. But many of the questions on this forum deal with problems with plaster, tile, epoxy etc. So the question is, why did makers go over to tools made of something other than another simple disk of glass?

I have used concrete cast into a disk shape and epoxied glass or ceramic

tiles to the surface. I polyurethaned the concrete to keep bits of concrete

from loosening and causing scratches. Works well.



#3 KI5CAW

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Posted 06 August 2022 - 12:19 PM

It occurred to me that using tiles leaves channels in the tool surface that would help keep the disks from sticking together.



#4 Scott E

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Posted 06 August 2022 - 01:39 PM

You can always cut grooves in glass with a diamond disc. I used a 10" glass disc with grooves (lent to me) for my 12.4" mirror years ago. But to answer your question, the reason people may elect not to use glass is cost and availability. This is especially true for large mirrors. I'm planning a 26" and the tool needs to be at least 18". For a piece of glass that's not destined to become a mirror, that's a lot of money.



#5 dogbiscuit

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Posted 06 August 2022 - 02:32 PM

Plaster tools are easy enough to make, but anything can be done incorrectly, especially the first time someone does something.  Same with other aspects of atm.  Learn by experience.



#6 KI5CAW

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Posted 06 August 2022 - 02:48 PM

Well, of course! I was thinking of the small mirrors in the under 10" range. Didn't think of trying to use a glass tool for a 20" mirror. Dogbiscuit, if I really get bitten by the mirror making flea, I'll be looking for your advice doggy.gif



#7 KI5CAW

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Posted 06 August 2022 - 02:50 PM

When I went off to college, Mom cleaned out the garage and tossed my teenage attempt at mirror making. Otherwise I'd still have those 6" disks!



#8 pjmulka

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Posted 08 August 2022 - 10:05 AM

Dental plaster is the way to go! It’s strong and waterproof and easily re-channeled if need be.
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#9 Stephen Kennedy

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Posted 08 August 2022 - 02:19 PM

I use the plate glass tool that comes with the Pyrex mirror blank when I order a kit.  While I enjoy grinding and polishing, I have no aptitude for and take no pleasure in fabricating things, so  not having to make a tool when the vendor sends me a perfectly good, ready to use one removes a messy and time consuming annoyance from making a mirror.



#10 Dale Eason

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Posted 08 August 2022 - 03:21 PM

Today it seems like makers commonly use plaster tools faced with tile. But many of the questions on this forum deal with problems with plaster, tile, epoxy etc.

There are very good instructions available on the net including the ones at gotgrit.com.  Which is what I used to make my 16 F5 mirror.  If you follow those instructions there need not be any questions.  Most of the questions I see are due to people not using those instructions or modifying them as they think fit.  There are many many good ways to do it.  So if one wants to do it a little different then they should ask.   But if you follow a set of instrucitons like I did then you should not need to ask.

 

Today with glass price high it is cheaper to use a tile tool in my opinion.

 

Dale


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#11 tommm

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Posted Yesterday, 11:01 AM

In addition to the above, with glass or tile you are expending energy grinding both the tool and the mirror blank. Some people use a metal ring for a rough grinding tool. I used a 10 lb dumb bell weight to rough the curve into a 22" blank. It goes faster due to most energy going into grinding the blank.  Likely wouldn't make as much difference on a small mirror because you don't have to remove as much material, even less if it is higher f number, so it goes pretty quick with about any tool material.




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