Setting glass - Butyl or Urethane? ... AAARG!!! - Page 4 - Chevelle Tech
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post #46 of 137 (permalink) Old May 31st, 12, 10:40 AM
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Re: Butyl or urethane... AAARG!!!

Some epoxies contain talc, so they're not 100% waterproof. So if urethane is supposed to go on epoxied bare metal, how is one addressing that issue? It's been stated you can't put urethane over finished topcoat. But topcoat is waterproof and many shops are installing glass over finished paint with no failures. Where's a glass tech with 2012 data on mandatory installation guideline documentation on new and repaired vehicles? I know that the existing urethane is supposed to be left in place after cutting out the old glass. That has not changed.

We'd get more information over Refinish Network than here. The ratio of pros and shop owners to hobbiests far exceeds that of this or a similar site.
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post #47 of 137 (permalink) Old May 31st, 12, 11:59 AM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by Raven1 View Post
Some epoxies contain talc, so they're not 100% waterproof. So if urethane is supposed to go on epoxied bare metal, how is one addressing that issue? It's been stated you can't put urethane over finished topcoat. But topcoat is waterproof and many shops are installing glass over finished paint with no failures. Where's a glass tech with 2012 data on mandatory installation guideline documentation on new and repaired vehicles? I know that the existing urethane is supposed to be left in place after cutting out the old glass. That has not changed.

We'd get more information over Refinish Network than here. The ratio of pros and shop owners to hobbiests far exceeds that of this or a similar site.
Well, here is a certified "glass tech" and I said what has to happen, bare metal, epoxy primer, then urethane, PERIOD. Many components from the manufacture like lift gates will even have the pinch weld covered in tape and you paint the gate, THEN remove the tape exposing the factory primer (epoxy? I don't know, but factory oked primer) before you urethane the glass in on that primer.

In ICAR class it is made VERY clear, epoxy over bare metal. We here at the shop have a company called "Verifacts" come by with spot checks and this is one of the things they check, that there is NO PAINT in the pinch weld where the urethane bed is to be.

Yes "Epoxy primer" quality has a pretty wide range, and as far as I remember GM doesn't have a specific part# epoxy they sell. They use a term like " use a quality epoxy" or something like that, leaving the door open to cover their tush.

They have the same recommendations for bonding fiberglass body structural pieces to the aluminum frame on a C5 Vette, epoxy primer over the aluminum and then the GM "urethane" (not sure of the actual material description) over that epoxy to bond the panel on.

"Water proof" has little to do it, it's all about the tensile strength (I guess that is what you would call it) my book on the subject from class is at home, I'll look at it tonight.

But anyway, the bond between the basecoat and clear coat is one of the issues, think about it. If you put a 1K single basecoat then clear over it, just how good is that bond? How about waterborne basecoat? You are relying on the integrity of waterborne basecoat to hold in a structural piece of the body? HUH? I don't care what urethane, butyl, elmers glue, if you put it on top of a waterborne base/clear, your bond is only as strong as the waterborne base/clear! THAT is the issue.

Urethaning a window in over the bc/cc is a BIG no-no and not one bit better than using Butyl. Don't be so down on butyl if you are advocating urethaning over paint!

And coolblue, the one problem with the OEM manual is that it is going to give part numbers for products that aren't available. I have a manual but forgot to check it after I read your post, I will tonight. Also, cutting the glass off the urethane and bonding the glass back to FRESH CUT urethane IS the number one recommendation in the industry. And that is exactly how it is done every day. We wouldn't expect a glass shop to shop to strip out all the urethane and primer and repriming it right? Well slicing the urethane bed in half and putting a bead of urethane over it then setting the glass is EXACTLY what is done and is the recommendation in the industry.

Brian

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post #48 of 137 (permalink) Old May 31st, 12, 12:04 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by CoolBlueGlow View Post
So, to summarize a number of the useful observations and conclusions contained in this thread, in no particular order of appearance or value;

1. When restoring window channels, Urethane can go over epoxy primer, does not require bare metal and does not play well with topcoats
2. Because of #1, overspray, topcoats, primer, etc. are to be avoided in the window channel, as they can contribute to leaks caused by poor bonding
3. rust issues in the A & B body GM products of the era may originate more from trim clips than leaky windows.
4. warranty and legal reasons prohibit professional installers from using butyl tape - but it may work fine on vintage A and B bodies. Use at your own risk.
5. GM used a sealant made by the Thiokol corporation (still around btw) Scott is still as grumpy as ever, but a useful source of information :-)
6. Several restorers have managed to use butyl tape successfully in their restorations - and can document long term success...but GM did not use tape.
7. The materials required to do a neat urethane job are available.
8. To do a urethane job, one cannot simply buy a tube of window sealant - other tools and materials are required - otherwise, the job will look inferior. These include setting blocks, sealant dams, the correct channel primer, and of course the correct sealant.
9. structural issues related to butyl taped glass are minor on A body cars, since they are frame under body designs, as opposed to uni-body designs.
10. 59 Ramblers had rubber seal set windows, not glue ins.
11. People tend to be more rude to each other in writing than in person

There... is that about it? Did I miss anything?



Cheers,

Keith
Number 1, let's be sure it is epoxy OVER bare metal. So bare metal IS needed.

Number 11, you look like hell wearing socks with those sandals.

Brian

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post #49 of 137 (permalink) Old May 31st, 12, 12:47 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by MARTINSR View Post
Urethaning a window in over the bc/cc is a BIG no-no and not one bit better than using Butyl. Don't be so down on butyl if you are advocating urethaning over paint!


Brian
Not once did I advocate using urethane on BC/CC. I stated in the 80's I used butyl and I used urethane over BC/CC. That urethane installation was done by a glass shop, not me. I assumed they knew proper procedure. Because I was the car owner, ultimately I'm responsible for verifying even a professional's work. But the installation never failed and I still have the car. I also stated shops do indeed use urethane over BC/CC. So it's my job to research what's correct even though I'm paying a shop to do my glass. If you read my posts on butyl, the main point is informing people butyl was not used originally and shops can't legally use it. At least not here anyway.

When a younger tech came to replace a windshield on a '95 Wrangler I asked him how he would do the glass in the Camaro next door. He said he would use butyl like originally done. Not a good answer.
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post #50 of 137 (permalink) Old May 31st, 12, 12:56 PM
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Re: Butyl or urethane... AAARG!!!

Are all the window channels on every new car free of paint and only the EDP coating exposed, thus leaving them ready for glass installation? I ask because looking at cars in a collision shop is no longer my business.

Last edited by Raven1; May 31st, 12 at 2:14 PM. Reason: sp
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post #51 of 137 (permalink) Old May 31st, 12, 1:09 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
Not once did I advocate using urethane on BC/CC. I stated in the 80's I used butyl and I used urethane over BC/CC. That urethane installation was done by a glass shop, not me. I assumed they knew proper procedure. Because I was the car owner, ultimately I'm responsible for verifying even a professional's work. But the installation never failed and I still have the car. I also stated shops do indeed use urethane over BC/CC. So it's my job to research what's correct even though I'm paying a shop to do my glass. If you read my posts on butyl, the main point is informing people butyl was not used originally and shops can't legally use it. At least not here anyway.
Sorry, my understanding was that you didn't worry about the BC/CC, again sorry.

I also have to make it perfectly clear on MY opinion. I said early that it MUST be bare metal with epoxy then urethane the window in. This is following the guidelines for late model uni-body cars as the auto manufacturers and glass industry has laid out.

I am still under the opinion that it is a choice on a 50 year old car as the difference between urethane and butyl is negligible when the rubber meets the road. We are talking about an old technology car and the glass isn't a structural part of the car like a late model uni-body car.

The ONLY issue when discussing the difference is the safety factor. Will the glass stay in the car in an accident, THAT is the only issue to discuss. I personally feel that if you hit something hard enough for properly used butyl allows that glass to come out, you are in deep trouble and the glass coming out is going to be the least of your problems.


As far as sealing, butyl tape then sealed with urethane will do the job. Heck, if the pinch weld is nice just the butyl will work alone. If you have leaks you have other problems, it isn't the product you used. Urethane will make up for other problems, now this is true! If the pinch weld has some rust pits that were sand blasted and epoxy primed it is flows MUCH, MUCH more than the butyl will so it will go down into those pits filling them. If weld seams are uneven, it will go down into the nooks and crannies filling them.


The learning curve for urethane is steep, it is sloppy messy stuff and can make a heck of a mess that is VERY difficult to clean up. I will have to do an updated "basics" on urethane.
But honestly, it has a very steep learning curve and can really bite you. Where as Butyl is a no brainer. It's a choice to make, that's all.

Brian

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post #52 of 137 (permalink) Old May 31st, 12, 1:16 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
Are all the window channels on every new car free of paint and only the EDP coating exposed, thus leaving them ready for glass installation? I ask because looking at cars in a collision shop is not longer my business.
Nope, not at all, they are painted. The difference is they are painted at the factory under the manufactures hand. Well now, how about the great clear coat peelers of the 80's were the windows set on THAT paint and clear, yep.

This is what we are talking about here, BS, the guidelines set are a cover SOMEONES tush, that is mostly what it is. The absolutely best way you could set a window is bare metal, epoxy primer and urethane, PERIOD, we know this, it is common sense.

But stepping back from "absolutely best" we find a VERY WIDE gray area, MILES wide. And there are miles upon miles of that gray area that is perfectly fine and realistic a quality as we spin on this rock in the middle of space.

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post #53 of 137 (permalink) Old May 31st, 12, 1:21 PM
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Re: Butyl or urethane... AAARG!!!

Ha! socks and sandals... VERY bad!

Yes, What I hope to communicate is that URETHANE does not require bare metal as its substrate - but rather epoxy primer properly applied over properly prepared bare metal - that's what I meant.


Keith

Is it just me, or is Scott in a very bad mood today?
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post #54 of 137 (permalink) Old May 31st, 12, 1:30 PM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by Raven1 View Post
If you read my posts on butyl, the main point is informing people butyl was not used originally and shops can't legally use it. At least not here anyway.
Okay, Butyl wasn't used originally, and shops are no longer allowed to use Butyl...


BUT, is butyl illegal (for a hobbiest on a 1960's/1970's Chevelle)?

Urethane is a better product it applied correctly, okay.

BUT, is butyl inferior to the original Thiokol product???

I have never seen a butyl-sealed windshield or back glass fall out (even in a severe collision or even a roll-over accident on an aquaitance's car- car and glass destroyed, but glass still attached)... On cars that I know used butyl, I have never seen a significant bonding problem (small leaks, but usually they were from a rusty substructure years after the glass was installed)...

On the flip side, I have seen numerous original glass that is no longer tightly sealed to the GM/Thiokol product, sometimes even at the glass/sealant interface ( NOT from body corrosion)...

Once you go RAT, you never go back...
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post #55 of 137 (permalink) Old May 31st, 12, 1:40 PM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by 1966_L78 View Post
Okay, Butyl wasn't used originally, and shops are no longer allowed to use Butyl...


BUT, is butyl illegal (for a hobbiest on a 1960's/1970's Chevelle)?

Urethane is a better product it applied correctly, okay.

BUT, is butyl inferior to the original Thiokol product???

I have never seen a butyl-sealed windshield or back glass fall out (even in a severe collision or even a roll-over accident on an aquaitance's car- car and glass destroyed, but glass still attached)... On cars that I know used butyl, I have never seen a significant bonding problem (small leaks, but usually they were from a rusty substructure years after the glass was installed)...

On the flip side, I have seen numerous original glass that is no longer tightly sealed to the GM/Thiokol product, sometimes even at the glass/sealant interface ( NOT from body corrosion)...
"Legal"? This isn't Australia where you have to have state ran shops do all your welding. This is America, have you seen a rat rod lately?



There are all kinds of guidelines in your state issued "Vehicle code book" available at your local DMV for a few dollars (at least here in Ca). Things like exact measurements about height of headlamps. But most stuff is VERY vague with terms like "must have adequate visibility" for a windshield. But there is NOTHING written at least in California about what glue is to be used holding a window in by a home hobbiest. Hell, any fool can go buy brake parts at Kragen and install them in their driveway, now THAT's a scary thought!
The "law" I personally don't think it exists. I am thinking it is more about guidelines that people "must" follow in the industry to COVER THEIR TUSH.

Over the long haul, will that original glass set in 1968 be better attached than a butyl tape job done last week? LOL, that is a heck of a question! I am thinking the butyl will kick it's butt! But that's just a guess. I know I have removed MANY windows originally set that I didn't even have to cut it out! NO KIDDING, the mouldings were holding it in! There was something like a foot or so that was still holding on, the rest of it was loose as a goose!

That big gray area is getting wider and wider.

Brian

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post #56 of 137 (permalink) Old May 31st, 12, 1:44 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
When a younger tech came to replace a windshield on a '95 Wrangler I asked him how he would do the glass in the Camaro next door. He said he would use butyl like originally done. Not a good answer.

several things...

First, the original GM method (when looking at an old car), "appears" to be butyl... Looking at an original Chevelle, the sealant doesn't look like urethane at all...

Second, when did urethane come into common practice for windshield replacements? I don't recall urethane until the 1990's... IIRC, glass installers and body shops were still using butyl in the 80's and 90's... I spent some time hanging out at various shops in my youth.



Is/was the thiokol product available to installers, readily available and competatively priced?

How is the performance of butyl compared to the Thiokol product? I know Brian addressed this regarding "original" versus new, but I am wondering "new" (1960's GM from the factory, versus the replacement with Butyl)?

Not even trying to suggest that Butyl is fine, just trying to figure if it WAS an adequate product, that has since been improved with urethane, etc...




I know 3M markets a buytl windshield ribbon (IIRC), and I assume it was developed as a suitable replacement with similar/adequate performance...

It would seem to me that 3M would have quit making or improved an inferior product...

Once you go RAT, you never go back...
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post #57 of 137 (permalink) Old May 31st, 12, 2:05 PM
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Re: Butyl or urethane... AAARG!!!

Butyl is still used today on many 2000's cars....on bolt in glass. Many Fords and Chryslers for instance use a piece of plastic that bonded somehow to a quarter window or sliding door glass in a mini van that has studs on it. Often this piece is like a frame around the glass and isn't "bonded" in anyway from what I see. You put butyl on this plastic piece that runs around the perimeter of the glass. You stick the glass in with the studs going thru holes in the body and then tighten up nuts on the studs squishing the butyl tape between the plastic and the body.

It's also used as a gasket on many Nissan tail lamps as well on a number of cars "moisture shields" that are behind the interior door trim panels.

And I am with you, butyl was how every window I did and the glass shops in town until sometime in the late nineties early 00's. While I was a paint rep from 95-00 and I wasn't paying attention all of a sudden when I got back into a body shop they were urethaning them in. As far as if the stuff GM used and Buytl can be compared, I don't think so at all. The stuff GM used was kinda like a urethane in that it got hard, butyl doens't. I can see the confusion people have in that it came off a roll from what I understand, that's why the string was in the middle. At least from what I understand or remember.

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post #58 of 137 (permalink) Old May 31st, 12, 2:27 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by 1966_L78 View Post
First, the original GM method (when looking at an old car), "appears" to be butyl... Looking at an original Chevelle, the sealant doesn't look like urethane at all...

Second, when did urethane come into common practice for windshield replacements? I don't recall urethane until the 1990's... IIRC, glass installers and body shops were still using butyl in the 80's and 90's... I spent some time hanging out at various shops in my youth.
What you saw may have been the dam.

I bought my first salvage truck in 1987, an S-15 rollover. Put a roof on it and urethaned the windshield in. I painted in with Cronar. Anyone remember that paint? I put urethane over the paint. Drove it for 5 years and no failures. I don't know what procedure was correct then and I was not schooled on the topic. I also used butyl at that time and had no issues.

I've also read of people laying a small bead of urethene, then laying butyl, then running a bead of urethane on top and setting the glass. The two are not compatible.
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post #59 of 137 (permalink) Old May 31st, 12, 3:15 PM
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Re: Butyl or urethane... AAARG!!!

Here is a 2011 Honda CRV and the instructions for this portion we have been discussing. This is right from the factory guidelines which I have access to on line.

8. Scrape smooth the old adhesive with a knife until there is a thickness of about 2 mm (0.08 in) on the bonding surface around the entire windshield opening flange: - Do not scrape down to the painted surface of the body; damaged paint will interfere with proper bonding. - Remove the rubber dam and fasteners from the body.

9. Clean the body bonding surface with a sponge dampened in isopropyl alcohol. After cleaning, keep oil, grease and water from getting on the clean surface.

10. If you are reinstalling the old windshield, scrape off the old adhesive, the clips, and the rubber dams from the windshield with a putty knife. Clean the bonding surfaces on the inside face and the edge of the windshield with isopropyl alcohol. Make sure the bonding surface is kept free of water, oil, and grease.


Factory paint then a primer was brushed on, then the urethane. HOWEVER, this is NOT the guidelines in the aftermarket. There's that gray area.



How about GM, this is what they say.

Note: If corrosion of the pinch-weld flange is present or if sheet metal repairs or replacements are required, the pinch-weld flange must be refinished in order to restore the bonding area strength. If paint repairs are required, mask the flange bonding area prior to applying the color coat in order to provide a clean primer only surface. Materials such as BASF DE15(R), DuPont 2610(R), Sherwin-Williams PSE 4600 and NP70(R) and Martin-Semour 5120 and 5130(R) PPG DP90LF SPIES/ HECKER 3688/8590 - 3688/5150 - 4070/5090 STANDOX 11158/13320 - 14653/14980 products are approved for this application.

I don't know all of them but checked and the Dupont is an epoxy.

Let's get this straight, there are LOTS of conflicting information between manufacturers. Chrysler says to put a backing behind butt welds, others say NO. They say don't bond on their quarter panel yet BMW has a guideline that says to bond on a friggin frame rail in a 7 series! We are talking ZERO welds or bolts, a frame rail that the front bumper is attached to, it's GLUED on when you replace it per factory guidelines.

Yep, a big gray area, REALLY big.

Brian

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post #60 of 137 (permalink) Old May 31st, 12, 4:20 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
I've also read of people laying a small bead of urethene, then laying butyl, then running a bead of urethane on top and setting the glass. The two are not compatible.


Now that makes no sense what so ever!

Brian

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