Advice Sought on Modifying a Glass Muller

[Lovegasoline]

Greetings,
I'm new to the forum, have never done any technical work with glass, and I've got a quick technical question. I'm a painter and I own a glass muller (i.e., a solid glass object used to 'grind' paint. For example, one places a quantify of powdered pigment on a frosted glass slab, adds linseed oil, then uses the muller to grind (disperse) the pigment into the oil).

My muller is about 4" in diameter at the base but I believe it has a manufacturing defect: there's a raised 'lip' on the base (see attached pics) about 1/16". The transition from the bulbous base to the bottom grinding surface should be smooth, with no 'lip'. Mullers sell for about $70 and I bought this a long time ago therefor returning it is not an option. I'd like to modify it rather than discard it. Modifying it entails removing about 1/16" from the bottom of the muller and I assume this would be peformed by sanding or grinding the base down a little (Belt sander? Surface grinder? Other?). Can anyone recommend the best method and or tools, used to perform this operation?

Even though I have limited funds, I'll more than likely take this to someone and have them do it, rather than do it myself. I live in NYC, in Brooklyn near Pratt Institute, although to the best of my knowledge Pratt does not have a glass department. There's a bunch of glass stores (autoglass, etc) near to me so I was thinking of taking it to one of those, but I'm not sure if they are used to dealing with something like this rather than with glass sheet/plate, so I want to know what to ask them (i.e., if they have the correct tools) to perform the job.

Alternately, if anyone knows a place in NYC that can perform this please do post up.

Any suggestions?

Oh, other than a six pack bro deal, any idea how much I should be charged?



Thanks a bunch!

[TarHallowGlass]

You could pay someone to lap it down or you can do it yourself by taking a piece of plate glass and putting carborundum powder grit on the plate and a little bit of H20 and moving your glass piece in a figure 8 pattern across the plate and grit until you remove the desired amount of glass. Hope this helps.

[Lovegasoline]

I use carborundum powder to frost the muller base and glass slab ... but I think it would take me about a month to grind that much off the muller by hand .

[menty666]

You need someone with a wet grinder. A stained glass shop would have one, so try to find them or a restorer.

Good luck.

[Matt P]

I use carborundum powder to frost the muller base and glass slab ... but I think it would take me about a month to grind that much off the muller by hand .

The woman who taught me to cast glass years ago used a potters wheel for her grinding, some water and carborundum powder on the wheel and you can make decent progress at it. Granted its still slow, but visible progress can be made doing that.

[poncho]

I'm in central NJ, you can bring/mail it to me and I can grind it for you.

[3musesglass]

Urban Glass right in Brooklyn has a very nice coldworking room. Ginormous wheels that use grit. It's been a while since I've been there.
http://www.urbanglass.org/

[Julian]

This would be simple to grind flat, using a flat lap wheel grinder.

[somewhere]

Another option:

Call any window glass company. They should all have a vertical wet belt sanders. It will take less then a minute to resurface. Ask them first if they have a wet belt sander then go show them the piece. I'm sure they will help.

[Greymatter Glass]

you don't want to use anything other than a flat lap on a muller. A belt sander would ruin it, they need a perfectly flat surface, a belt sander would risk rounding it out some, or faceting it, unless the belt was wider than the muller and had a solid back behind the belt (then it might work...)

I have made smaller mullers, they take a few minutes to grind. To refinish that one would take 4 or 5 minutes, most of the time spent setting up the machine and getting the water flowing.... I wouldn't charge anything if the person asking was polite and willing to wait a few minutes. At any rate, I'm sure you can find someone willing to do it on the cheap, like slip 'em $10 and they'll get it done.

[somewhere]

Honestly you could just go buy a piece of sand paper from any hardware store and lay it on a flat surface and start sanding. This isn't rocket science it just has to be flat. Look for silicon carbide paper.

Seems futile to argue but a wet belt will work fine. I use these machinea daily. Even without a flat platen which if you own a 106" abrasive welt belt you most likely do. A tight belt brings a nice flat surface to a paper weight in less then a min. You are correct it won't be perfect but it will be flat. This isn't presicion lapping. Maybe next time post your concerns without dismissing others. Linishing has a great history in cold working glass.

[steak351]

i made some of them for the flat glass people at my school, just a big maria, and grind it on a rotating flat stone, i made also worked ones with implosions at the top,..looked like dillys

[menty666]

That'd be a lot of glass to remove by hand though.

[Lovegasoline]

Thanks for all the great replies.

Btw, the muller does need to have a flat bottom: when making oil paint in conjunction on a grinding slab, it can generate some seriously heavy suction at times.

From what I can distill from all the replies a flat lap wheel grinder, wet, seems to be the generally preferred method.
I've never been to Urban Glass, it sounds like an exciting place. I'll see if I can make it over there, or if not maybe there's some other well equipped glass shops in Brooklyn. Is a flat lap wheel grinder something an autobody glass shop, or window glass shop, would likely have? Or, is that sort of machinery more specific to a different sort of glass business?

PS: poncho, thanks for your offer ... if I can't get this taken care of locally, I'll take you up on your offer.

[3musesglass]

I forgot about this place, also in Brooklyn. They may have flat laps too. Not sure, it's been ages since I've been there too.
http://www.tecnoboro.com/

[Greymatter Glass]

A flat lap is not something you'd generally find in an auto or residential window glass shop, but stranger things have been known to happen.

In addition to Urban glass you might also try Brooklyn Glass (http://www.brooklynglass.com/index.htm) they have coldworking facilities and could probably help you.

[Julian]

Is a flat lap wheel grinder something an autobody glass shop, or window glass shop, would likely have? Or, is that sort of machinery more specific to a different sort of glass business?

They're used primarily in lapidary arts, actually. Not sure what type of lapidary businesses might be in NYC who would let you use their equipment, though.

[smutboy420]

I think He meant a place he can take it to that would have the equipment to do the job for him.

[somewhere]

I was talking about a flat platen that mounts on a verticle wet belt. 4" x106" verticle wet belt sanders are about as common in a commercial flat glass shop as glass is. Most of these trades use roller platens for edging sheet glass. A flat platen is made of graphite, steel or plastic and is a flat surface that runs behind the belt. I can post links if you can't wrap your head around how that works.

Ideally yes a flat lap is the tool for the job but as I posted linishing is another option. I also said this could be lapped by hand and it can without as much effort as one may think. I know two artists that hand lap all their components for their sculptures. with loose grit on a piece of flat glass. Start with a 60 or 80 then go up from there. I have ground and finished thousands of pieces of glass.

Best suggestion by far IMO is visit the local college's glass shop. If nothing else I think it would be a learning experience.

[Julian]

Take it outside and rub it on the sidewalk?