auto glass?

[benjamin]

I have an unlimited source for auto glass (chances are you do too, those discount windshield places get rid of a dumpster a day). I'm told the laminated (not tempered) stuff can be cut with a dremel + diamond cutting wheel. Anyone have any experience? Suspect it may be more trouble than it's worth (even if it's cut-able, might be junk optically after time on the road), but if it works, would be a nice option for portable scanners...

[daniel_reetz]

The increased strength would be good, and the source is damned interesting.

It's not directly comparable but my experience just trying to sand the cut edges of "double strength" glass with a dremel+diamond coated bit were SERIOUSLY time consuming and didn't end up with a nice finish. I ended up using a wet piece of 120 grit on a marble cutting board to get nice, flat beveled edges.

[benjamin]

well, i'm gonna try to pick some up this weekend and experiment. I'm not too worried about rough edges, as the plan is to make a hinged wooden platen frame and route a channel for the glass. will report back...

[phaedrus]

Hi, I wonder if you can get flat glass this way though? These days I would have though that almost all autoglass is curved somehow (at least the laminated stuff) & I'm not sure that'd work all that well for a book imager.

I have flat glass from my VW's, Bedfords & various 4WD's but they're all toughened which you'd never cut successfully.

Cheers, P.

[benjamin]

i'm thinking side windows; and sliding rear panels from trucks. i met the guy when he repaired a chip in my '78 F150 (yeah, i coulda done it myself, but I was buying the lifetime warranty). He says he does a lot of older vehicles (thus hopefully a lot of older glass)... I'm not hugely optimisic, but we'll see.

I've started wondering whether a glass platen is even strictly speaking necessary. Because the books we're dealing with are all one size, I've started playing around with empty frames... seems like with enough weight around the edges the glass might not even need to be there... though this may require more care in placement.

I'm still waiting for camera delivery, though, so this is all hypothetical...

[daniel_reetz]

I haven't had much time to share it here, but I've been working on a glassless portable design. StevePoling suggested some things that got me fired up about the idea. And the regularity in your case is definitely something to exploit... just can't wait to see what you come up with.

[spamsickle]

I apologize for so often being the guy who questions whether an innovation can be made to work. In the case of auto glass, my objection has to do with the thickness of the glass, which once again is going to limit your coverage of the "gutter" of the book -- the inner margin between the two pages. In many of my books, I've already lost image to the bookbinder who pulled a bit of a two-page map into the spine, for instance. Any thickness of glass will add to this loss in such books, and the thicker the glass, the worse the loss.

On the other hand, this glassless idea seems like it might have potential. In grabbing the first dozen books nearby, it seems that the smallest top/bottom margin in any of them is a quarter of an inch. If one can work out a way to make the positioning of the platen precise enough as it's raised and lowered, I expect 3/16 of an inch might be enough real estate at the top and the bottom to hold a book flat.

Dan, I know you're concerned about reflections, but I've found that the anti-reflective glass I got from the art supply store made that a non-issue for me. The only reflections I get are from the acetate covers on some of my books, so that wouldn't be my reason for going glassless. For me, the advantage would be the additional coverage it would make possible in that gutter.

I built a box around my platen to keep the frame that holds the glass from spreading in the direction of the book's height. I think a box around the platen might still be a useful design element in a glassless platen, but my "floating" box-within-a-box design is a long way from placing the platen precisely enough to attempt glassless scanning. Plus, not having a fixed format of books I plan to scan, for me the platen design would need to be adjustable to match the height of each book. Ideally, I'd like the platen to settle over the outside edges of the pages to position itself, but at the front and back of the book there are no pages to settle around on one side of the book.

I bought a bunch of threaded rod that I didn't end up using to build my 2nd scanner. I might be able to use them in a 3rd-generation book-height-adjustable glassless scanner.

Something to think about, anyway.

[jakegaisser]

I went to google maps and typed in glass "zip code here" and it pulled up every business in my area that has to do with glass. I called around asking if they cut 1/8 glass or picture frame glass. I found a glass shop in town that sells it for $2.00 per SQ FT so I got two 12x16 pieces of 1/8 glass cut and ready to go for only $6 or so.

[daniel_reetz]

That's excellent, and about half the price I pay around here. Did they bevel the edges for you?

[jakegaisser]

they dont feel sharp, so maybe? it doent have an angle edge like a picture frame glass might... also there were more expensive places in town, one of the shops I called was going to charge twice as much for the same size pieces of glass, so if money is ever an issue its good to call around and get prices from the different shops.