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Photo Forum / Film Photography / Large Format / April 2004Rubbing compound? Which one for ground glass?
I'm likely going to order a scale from a jewellery supply house [best price for the accuracy needed] they also sell quite a few different compounds for polishing. I know somebody awhile back mentioned these could be used for making a ground glass but which one? They've got a whole bunch of rouge. Red,blue,green etc. They've got tripoli compound. Ruby powder. Pumice powder. Too many choices. Thanks Nick On 4/23/2004 9:54 AM Nick Zentena spake thus: > I'm likely going to order a scale from a jewellery supply house > [best price for the accuracy needed] they also sell quite a few different > compounds for polishing. I know somebody awhile back mentioned these could > be used for making a ground glass but which one? They've got a whole bunch > of rouge. Red,blue,green etc. They've got tripoli compound. Ruby powder. > Pumice powder. Too many choices. No, no, no: those are polishing compounds. Much too fine. You'll end up with polished glass. What you want is *grinding* powder. Simple silicon carbide powder is all. I use 1200 grit to get a finer ground glass than most. You can get this stuff in grits from less than 80 (too coarse) all the way up to 4000 or more. Just for reference, ordinary valve grinding compound (silicon carbide in paste form) is about 220 grit, which makes adequate ground glass, if a little coarse. I'd recommend 400 or finer. Buy a couple different grits and experiment. At 5 minutes max. per piece of glass, not a big investment in time.  SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress There I knew it ... > No, no, no: those are polishing compounds. Much too fine. You'll end up with > polished glass. [quoted text clipped - 7 lines] > coarse. I'd recommend 400 or finer. Buy a couple different grits and > experiment. At 5 minutes max. per piece of glass, not a big investment in time. They've only got silicon carbide on wheels. I guess I'll go with the valve compound. Thanks Nick On 4/23/2004 11:21 AM Nick Zentena spake thus: >> No, no, no: those are polishing compounds. Much too fine. You'll end up with >> polished glass. [quoted text clipped - 10 lines] > They've only got silicon carbide on wheels. I guess I'll go with the valve > compound. Don't know who "they" are: your local hardware store? No surprise. However, the stuff *is* available. Here's one supplier found with a few minute's googling (500 grit): http://www.tools-plus.com/h-dsc500.html I bought mine at a Japanese woodworking supply store in Berkeley (Hida Tool, http://www.hidatool.com), so I know they have it in several grits, including some much finer than the 1200 grit I got, but I can't find it on their website. You could give them a call; they're very nice people. Or you should be able to find it from a large woodworker's supply place. The valve grinding stuff'll work, but as someone else pointed out, it's pretty coarse. You can do better. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress > On 4/23/2004 11:21 AM Nick Zentena spake thus: > [quoted text clipped - 27 lines] > The valve grinding stuff'll work, but as someone else pointed out, it's pretty > coarse. You can do better. Could you detail the rest of the procedure, please? And will this help me attain a bright screen such as those sold by Maxwell Precision Optics and Beattie? SignatureRegards, Matt Clara www.mattclara.com On 4/25/2004 4:44 PM Matt Clara spake thus: >> On 4/23/2004 11:21 AM Nick Zentena spake thus: >> [quoted text clipped - 33 lines] > attain a bright screen such as those sold by Maxwell Precision Optics and > Beattie? Here's how to do it: 1. Put a piece of glass larger than the one you want to make ground on a flat work surface. Both this piece and the workpiece need to be as flat as possible, so no old wavy window glass! Ordinary window glass is fine (the thicker the better, so get "double strength", at least here in the US). 2. Sprinkle a little of the silicon carbide powder on the glass (or put a little valve-grinding compound on it). Sprinkle a little water on the powder. 3. Put the glass you want to grind against the first piece of glass and grind away. Use nice big circular and figure "8" motions. Do this for a few minutes, then take the glass off, rinse off the abrasive paste and examine it. Make sure there aren't any low spots, which will show up as clear, unground spots. If all is ell, continue grinding for a few more minutes. Check, repeat as needed, and stop when you have a nice consistently-ground piece of glass. One thing to be careful of is not to get too much abrasive on the *top* of the glass, as it can scratch what should be the polished side of the ground glass. It's OK if some gets on, just avoid rubbing it in with your fingers. As for your other question, no, I would never make any claim that the resulting glass will be as bright as those screens. Fine, yes. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress > And will this help me > attain a bright screen such as those sold by Maxwell Precision Optics and > Beattie? No. They work by scattering less light, which leads to a brighter hot spot, and then they use a fine-lined fresnel to even out the illumination. Beattie adds anti-reflective coating on the back of glass. You could experiment by using a light grind on the glass and a secondary fresnel. Finding the right fresnel would be the hard part, as the one sold as reading magnifiers are way to coarse. They even the light out but they obscure detail. -Peter > I'm likely going to order a scale from a jewellery supply house > [best price for the accuracy needed] they also sell quite a few different [quoted text clipped - 5 lines] > Thanks > Nick Someone else in this group mentioned they use 1,200 grit silicon carbide, then I read the aluminum oxide is better, with that I would get a very fine grit though I don't know how fine it gets. Or better yet try to find the acid used for etching glass, whatever it's called. Dangerous as all hell I would suggest ... Alex >> I'm likely going to order a scale from a jewellery supply house >> [best price for the accuracy needed] they also sell quite a few [quoted text clipped - 11 lines] > yet try to find the acid used for etching glass, whatever it's > called. Dangerous as all hell I would suggest ... Hydrofluoric acid. If you insist, try, instead a solution of ammonium bifluoride in water. Since you do not want both sides etched, coat one side with paraffin first. Of course it may be some trouble getting it off first. Ammonium bifluoride in water is not something to put your hands in either. It seems to me it would be a lot easier to just buy a ground glass. Signature.~. Jean-David Beyer Registered Linux User 85642. /V\ Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 14:20:00 up 15:02, 4 users, load average: 4.49, 4.16, 4.04 >Since you do not want both sides etched, coat one >side with paraffin first. Of course it may be some trouble getting it >off first. Microwave ? Hot water ? Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email > Hydrofluoric acid. If you insist, try, instead a solution of ammonium > bifluoride in water. Since you do not want both sides etched, coat one [quoted text clipped - 3 lines] > > It seems to me it would be a lot easier to just buy a ground glass. You might want to try one of the glass etching kits that are sometimes available in art and craft stores. I don't have any to recommend, but you might check around. KB > You might want to try one of the glass etching kits that are sometimes > available in art and craft stores. I don't have any to recommend, but you > might check around. > > KB This doesn't work very well. I tried numerous techniques. No matter what I did, the results were uneven. I took the samples to the local "art glass" people. They said, "Wow, that's much better than we could do." But it wasn't near good enough. Either find the appropriate powdered abrasive, or buy good quality ground glass. It's really not very expensive. Valve grinding compound makes a crappy ground glass. -Peter > powdered abrasive, or buy good quality ground glass. It's really not > very expensive. Valve grinding compound makes a crappy ground glass. Couldn't it be useful as a first step, and then polish it with finer grades? I've not ground my own, as you can tell, but might try it the next time I need a replacement. Even if you only use one finer grade for a final polish/grind, wouldn't the coarser valve compound make it easier? Or is the whole job too short and simple to bother with this? On 4/24/2004 3:50 PM MikeWhy spake thus: >> powdered abrasive, or buy good quality ground glass. It's really not >> very expensive. Valve grinding compound makes a crappy ground glass. [quoted text clipped - 4 lines] > polish/grind, wouldn't the coarser valve compound make it easier? Or is the > whole job too short and simple to bother with this? Yes, <groan>. As I've been trying to say, the whole job is too short and simple to bother with such extra steps. Just use a finer grit (I use 1200 and get very nice results which rival commercially-available ground glass). The whole thing takes about ten minutes from start to finish, including cleaning the glass when done. The only other essential thing to have is another piece of glass which is at least as flat as the glass being ground. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress Go down to your favorite auto supply house and get a tube of valve grinding compound. Last one I bought was $1.59. Use that. Regards, Marv > I'm likely going to order a scale from a jewellery supply house > [best price for the accuracy needed] they also sell quite a few different [quoted text clipped - 5 lines] > Thanks > Nick >Go down to your favorite auto supply house and get a tube of valve >grinding compound. Last one I bought was $1.59. Use that. I used regular valve grinding compound and found it to be WAY TOO COARSE... I don't recommend it at all... I couldn't see what I was trying to focus on, and a loupe made it worse!! Doug > I'm likely going to order a scale from a jewellery supply house >[best price for the accuracy needed] they also sell quite a few different [quoted text clipped - 5 lines] > Thanks > Nick Try 800 grit emery cloth. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email > I'm likely going to ... a jewellery supply house ... they also sell > ... compounds for polishing ... ground glass but which one? The Auto parts store carries 'Rubbing Compound' and 'Polishing Compound'. Rubbing compound is white and is used for removing scratches from auto paint - it leaves behind a 'scoured' surface. Polishing compound is red and is used to polish a rubbed area to a high shine (or to try and shine dull auto paint). I would use the white rubbing compound. My 1 lb tin says $1.50 on it, but it is most likely 30+ years old. Anyway the stuff is cheap, and if it doesn't work the way you want on glass, you can always use it on your car. Valve grinding compound is for _grinding_ metal, wouldn't advise. SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ On 4/24/2004 7:00 AM Nicholas O. Lindan spake thus: >> I'm likely going to ... a jewellery supply house ... they also sell >> ... compounds for polishing ... ground glass but which one? [quoted text clipped - 11 lines] > > Valve grinding compound is for _grinding_ metal, wouldn't advise. Wrong again. Valve grinding compound (which is indeed made for grinding metal) is *exactly* what you should use to make ground glass. (Though as I've pointed out, too ma ny times, it's a little on the coarse side.) "Rubbing compound" (aka polishing compound) is for just that--polishing--and will not produce a ground surface, no matter how hard or long you rub. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress Yeah, Nick, but it does make nice ground glass in about 10 minutes. Regards, Marv >>I'm likely going to ... a jewellery supply house ... they also sell >>... compounds for polishing ... ground glass but which one? [quoted text clipped - 11 lines] > > Valve grinding compound is for _grinding_ metal, wouldn't advise. > Yeah, Nick, but it does make nice ground glass in about 10 minutes. Why don't you try white rubbing compound and I try valve paste and then we can both talk intelligently on the subject. Or not. SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ > >>I'm likely going to ... a jewellery supply house ... they also sell > >>... compounds for polishing ... ground glass but which one? [quoted text clipped - 11 lines] > > > > Valve grinding compound is for _grinding_ metal, wouldn't advise. On 4/25/2004 10:06 AM Nicholas O. Lindan spake thus: >> Yeah, Nick, but it does make nice ground glass in about 10 minutes. > > Why don't you try white rubbing compound and I try valve paste and > then we can both talk intelligently on the subject. Or not. Well, I can tell you that you'd be wasting your time; you'd end up with a slightly less polished piece of glass, but nothing remotely close to ground glass. I know, because I use white rubbing compound (automotive) all the time to polish stuff. But I also use valve grinding compound (also automotive) to make quick & dirty ground glass. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress I've done the valve grind route in making GG for my 45 Busch. The whole technique is so trivial it does not merit the "science project" approach. If you want to use white rubbing compound, go right ahead. Regards, Marv >>Yeah, Nick, but it does make nice ground glass in about 10 minutes. > > Why don't you try white rubbing compound and I try valve paste and > then we can both talk intelligently on the subject. Or not. |
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