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Glue chip glass problem

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Robert Schwieger
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Location: Nebraska

Glue chip glass problem

Post by Robert Schwieger »

Working on 13"x72" 1/4" plate glass. Glass prep included the usual. Vinyl mask was hand cut. Local stained glass (reputable) blasted with silicon carbide. Glass cleaned again thoroughly with Bon Ami. Glue prepared in usual manner and applied to warm glass after the asphaltum step to contain the glue. Room temp for six hours followed by overnite low fan. Into a warm compartment with dehumidifier since we have high humidity. After six hours the glue easily came off in full pieces without any chipping. Cleaned everything up and rebrushed the asphaltum and mixed up a NEW batch of a DIFFERENT brand of glue (one which worked on previous projects). Same steps regarding warmth, fan and dehumidifier. Same result. The glue was heated correctly so this doesn't seem to be the problem. The only question mark seems to be the blasting. Could it be the culprit? Too smooth and no tooth to the glue areas? If this is the problem, what are the alternatives to save this project? Although I don't want the effect, the etched glass areas would work except for one very small (quarter inch) chip. The gilded chip would be the best outcome. Is it possible to "save" this rather large project? Thanks. Bob
Robare M. Novou
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Re: Glue chip glass problem

Post by Robare M. Novou »

Have you Chipped Glass Before? Sorry, had to ask.

If so, did you do anything different with this project/process?

Is the glass tempered?

What was the grit size of the silicon carbide?

What is the strength of your glue?

Got any pictures of the dried glue on and off the glass, that you can post here?

You might want to get the blasted area wet prior to pouring on the glue.

I get the feeling your glue is not thick enough.

RMN
What's On Your Book Shelf ?

http://www.milwaukeesignworks.com
Robert Schwieger
Posts: 123
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Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

RMN and others,

I have successfully gilded glue chipped glass projects but this is a first that the chip did not occur. The pieces of dried glue came completely off without any fractures on the glass or the glue. I did omit the fact that I personally always used 220 aluminum oxide with good results. The only difference in this project was that I subcontracted the blasting to a local glass studio and I have discovered that they used silicon carbide starting about 200 grit and RECYCLE the blasting material with it being upwards of 400 grit at this time. Perhaps this is the problem...too fine....no tooth for the glue to adhere to.
This is just a shot in the dark but since two thirds of the vinyl mask is in place could I reblast with the 220 grit aluminum oxide to establish a surface similar to starting with the aluminum oxide on new glass. My science knowledge base is low so I appreciate the thoughts of those of you have the deeper knowledge. Again THANKS. Bob
Robert Schwieger
Posts: 123
Joined: Wed Feb 07, 2007 12:38 pm
Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

RMN and others,

I have successfully gilded glue chipped glass projects but this is a first that the chip did not occur. The pieces of dried glue came completely off without any fractures on the glass or the glue. I did omit the fact that I personally always used 220 aluminum oxide with good results. The only difference in this project was that I subcontracted the blasting to a local glass studio and I have discovered that they used silicon carbide starting about 200 grit and RECYCLE the blasting material with it being upwards of 400 grit at this time. Perhaps this is the problem...too fine....no tooth for the glue to adhere to.
This is just a shot in the dark but since two thirds of the vinyl mask is in place could I reblast with the 220 grit aluminum oxide to establish a surface similar to starting with the aluminum oxide on new glass. My science knowledge base is low so I appreciate the thoughts of those of you have the deeper knowledge. Again THANKS. Bob
erik winkler
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Re: Glue chip glass problem

Post by erik winkler »

Bob!

Rule one: Do not use contaminated grit.
If I use aluminiumoxide, I use the white (cleaned/pure) aluminiumoxide.
This was thought to me by master Dave.
If the grit was used for removing paint, wood or whatever; the least bit of oil-contamination in this gritt WILL repell the glue!

Erik
Realizing we are in the 2nd renaissance of the arts.
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Still in the learning phase ;-)
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Ingrid Mager
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Re: Glue chip glass problem

Post by Ingrid Mager »

Hmmmmm.......if it is indeed contaminated.....
If you are using a vinyl mask, then it is almost for certain a petroleum based adheasive, (as is the asphaltum), so if it were me, before trashing the piece, I think I would try cleaning with denatured alcohol first and reblasting. Maybe lacquer thinner also could work...anything that won't disolve the petroleum based glue. Worth a shot.

Also, it is possible to use a scribe to hand etch the glass prior to glue-chipping. That seems to tedious, but if you are trying to save the piece, well, there might be something to it.

~Inga
Last edited by Ingrid Mager on Tue Jun 15, 2010 4:59 am, edited 1 time in total.
Ingrid Mager
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Re: Glue chip glass problem

Post by Ingrid Mager »

I think a little coarser than 220 is probably better.
Whether that will make the difference you need, I don't know. Probably contaminated like Erik suggests.
~inga
Robare M. Novou
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Re: Glue chip glass problem

Post by Robare M. Novou »

Has the Stained Glass Shop that blasted your piece, ever chipped glass on their own before?

Or do they just do the Frosted Glass Blasting Only?

I was thinking that there might be some excess oil in their air lines.

Or...blasting with a grit finer than 220 does not give enough "tooth" for the glue to adhere properly for chipping.
Which is something I don't recall ever being discussed before, as to how fine can you blast before there is no longer the optimal tooth for the glue to grab.

220 may be that limit, and it can't be "used" 220, it must be "new" 220.

I personally have always used "new" 220. With good results.

Do they even sell a 400 grit sand for blasting?

Have it re-blasted with "new" 220....and then get in touch with BP for some oil dispersant (Dawn for Dishes) to use in your glass cleaning water, prior to your applying the glue.

RMN
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Danny Baronian
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Re: Glue chip glass problem

Post by Danny Baronian »

Bob,

there are a few things you can elimate as problems. One is silicon carbide. Silicon carbide does not break down like other media. Unused, under a microscope it has sharp edges, as it's used it fractures and becomes smaller but still retains the same sharp edges and the same properties as new media.

It only becomes useless when it has been used over a long period of time, and will far outlast aluminum oxide. Aluminum oxide breaks down at a faster rate, and diminishes in size/grit as well as aggressiveness.

What else does the shop do that blasted the glass, have you discussed the problem with them? If they're using 220 grit silicon carbide, it will have the same properties until the material has been used up.

As for recycling, everyone recycles or re uses their media. If you dump the media after each use it would not only be unnecessary, but expensive. Recycle or re use, whatever you want to call it, use the material until it's broken down to the point of not doing the job or through contamination.

How old is your glue, has it been sealed well? Have you tried blasting a new glass sample and applying the glue? The problem could be in your glue, not with the glass your working with. Time to do a test.
Danny Baronian
Baronian Mfg.
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Robert Schwieger
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Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

Thanks to all the great suggestions. I haven't abandoned the project yet. The only variable appears to be the blasting material. I am in the process of degreasing the previously silicon carbide blasted area(s) by the subcontractor and I will try re- blasting with the 220 Aluminum Oxide that I have had great success with in previous projects. I will share the results, good or bad here. Thanks again. Bob
Ingrid Mager
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Re: Glue chip glass problem

Post by Ingrid Mager »

There are industries that do NOT recycle their grit, but it is notvery common. I used to get #30 SiC at Spokane Abrasives for very little money for just this reason. The company using it needed SiC of a certain mesh, and after that could not use it anymore for their particular use, and sold it back to the abrasive house.

SiC and AO are typically sold in meshes of about #16 to #1200. Although typically considered more of a polishing grit above about #280, I have blasted with AO sizes up to #600 trying to emulate the look of acid etch. I couldn't get the same results. The etch was very fine, but lacked the dark tone you can get with acid etch, not matter how lightly I tried to frost. (#500 or so is typically used in air erasers...some folks also etch with air erasers for detailed areas)
----------------
As far as size goes, SiC actually breaks down quite quickly, even though it is harder than AO. But because of HOW it breaks down (silicon carbide has a blocky grain shape that splinters and remains sharp), it maintains its cutting ability as Danny suggested.

AO, on the other hand, breaks down in size more slowly, but gets more rounded and loses its cutting ability as it is breaking down.
----------------
There is another difference, though, and that is in HOW the two different mediums attack their surface. AO tends to more fracture the surface, whereas SiC tends to grind away at it. In the monument industry, this fracturing of the surface renders a whiter white which is used in the tiffany windows. (frosted areas). I can assume (but can't state for a fact) that because of this nature, the AO will yield a surface that is a little more prone to grip by the hide glue, all other factors being equal. I can also assume that a coarser grit SiC will render a gripping surface that is commensurate with a finer grit AO, but this is only theory, and not something I can give numbers to.

Although pain silica sand can actually cut glass quite nicely, it quite literally pulverizes as it hits the surface, and breaks down so quickly, it is hardly worth recycling more than once when blasting hard surfaces. I found the recent test comparing AO and plain silica sand interesting. I have used silica for glue chip prep before, and did not get the somewhat grainy appearance that Larry did. I suspect it is probably because I began with a 30/40 mix instead of a finer one, and got a coarser etch.....

Since steel shot will fracture a rock's surface even better than AO, I have to wonder what the difference would be in preparing a glass surface for Glue chip with it, instead of AO.
-----------------
When I get my shop put back together, I will run a slew of tests with all other elements being consistent and will post PIX of my results.

~Inga

PS - Another tidbit is that there are some folks who periodically, quite literally "cook" their grit in kettles to render impurities out of it, and I am assuming that grease and oils would be amongst those impurities.
Anthony Bennett
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Re: Glue chip glass problem

Post by Anthony Bennett »

I look forward to you getting your shop back up and running Ingrid and doing these tests.
David Slade
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Re: Glue chip glass problem

Post by David Slade »

Ingrid Mager wrote:Hmmmmm.......if it is indeed contaminated.....

Also, it is possible to use a scribe to hand etch the glass prior to glue-chipping.

~Inga

This hand etching technique sound interesting, Ingrid.
Robert Schwieger
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Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

Haven't abandoned the project. Update: Cleaned all blasted areas with acetone and then Bon Ami and complete rinse. Although tedious, used an electric engraver over the blasted areas. Applied glue and followed the usual procedures. Outcome: Chipped well except for one five square inch spot. Tried another glue application to this area and the result is a very small chip more like pebbles than chips. I could probably get by with this but it is noticeable to me and I am sure, to other artists, a flaw. My question here to the experienced glass artists is "would it be too risky to try a third chip over this stubborn area to produce the more desirable chip or does continued chipping simply encourage the formation of smaller pebble like textures?". I would like to salvage this large piece (13"x72") and appreciate the advice. Bob
Roderick Treece
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Re: Glue chip glass problem

Post by Roderick Treece »

I am wondering about this step and why you would do this,
" Glass cleaned again thoroughly with Bon Ami."

There is no reason to clean the glass after blasting.

Roderick
Robert Schwieger
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Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

The cleaning step with Bon Ami after the subcontractors's blasting was intended to remove any residue that may have been remaining from the contractor's contaminated pressure system and I thought that it would help me determine the original problem with the glue not adhering to the blasted area. Bob
Roderick Treece
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Re: Glue chip glass problem

Post by Roderick Treece »

Bob,
Cleaning it seems to me to be the only thing that may have been a problem . Just simply blowing it off works fine for me.

This part doesn't make sense to me "I am in the process of degreasing the previously silicon carbide blasted area(s) by the subcontractor "

Why would the blasted area be greasy? Does he sandblast dirty motor parts?

Silicon carbide does a fine job of etching for chipping.
Doug Bernhardt
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Re: Glue chip glass problem

Post by Doug Bernhardt »

I'm in agreement with Rod. I have never had an issue with chipping and have never gotten worried about excessive cleaning. The sub-contractor I use only breaks the surface of the glass and he also recycles his aluminum oxide. They are a stained glass shop and buy their chipped glass from a production factory. So it can only be 1/ blasting too fine(although next to impossible) 2/ glue not correct (very likley) or 3/ creating some barrier in between the glue and glass or four ...buggering up something we couldn't imagine,overlooked or forsee. I'd go through the whole process like a science to work out what the heck happened. This all fits into John Studden's theory about work flow. There's sign time and then gold glass time. Seems to me the later is the hardest for an accountant to work out ;=/
Robert Schwieger
Posts: 123
Joined: Wed Feb 07, 2007 12:38 pm
Location: Nebraska

Re: Glue chip glass problem

Post by Robert Schwieger »

I have worked through the possible contamination. My primary concern with this piece is that after a second chipping, of which 95% was successful, I am still not pleased with a small remaining section (1 inch by 5 inches) that chipped with a different chip. A chip that was quite like small pebbles and to me, quite enough different from the remaining successful chipping that I am considering a third chip only in this small area. My question is "does repeated chipping of an area produce a larger chip or does one run the risk of the small pebble-like texture become smaller and what is the possibility of glass breakage on this 13"x72" piece". Your wisdom is greatly appreciated.Thanks again, Bob
Larry White
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Re: Glue chip glass problem

Post by Larry White »

There shouldn't be any problem in chipping that undesirable area again.
As with all chipping, there is really no way to predict the outcome.
My guess, that if applied correctly, a third pass would mostly remove
the small "pebbley" chip, and replace it with the desired chip pattern.

One way to find out, heh?

I've rechipped small "problem" areas before. I painted a 1/2" outline around
the area with asphaltum, then flowed the glue into this area with the
squeeze bottle technique. It's worked fine for me.

I've also noticed, that defects that occur at a particular step of a project,
seem to greatly deminish as the subsequent steps are executed and the
project is finished. After 4 or 5 years, I don't see the defects anymore! :P

-WB



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