Setting glass - Butyl or Urethane? ... AAARG!!! - Chevelle Tech
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post #1 of 137 (permalink) Old Mar 16th, 12, 3:30 AM Thread Starter
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Dave
 
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Setting glass - Butyl or Urethane? ... AAARG!!!

I feel like I have read it all when it comes to butyl tape versus urethane... My glass guy is good, though I don't trust him like I trust myself. I meticulously test fit, measure. and plan before I do anything. He just slaps glass in its place as quick as he can and then on to the next job... My biggest concerns with the urethane is the difficulty of cutting the glass out if job was done wrong, or windshield cracks and needs to be replaced in the future, urethane ooozing onto places it doesn't belong... Also the set height can affect moulding installation... On the contrary my only concern with the butyl is whether or not it is safe for a windshield? Never heard of a windshield dislodging from hard braking or a wreck??? Spent 3 years building this beast, any input is greatly appreciated!!!
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post #2 of 137 (permalink) Old Mar 16th, 12, 8:12 AM
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Re: Butyl or urethane... AAARG!!!

Dave, I'm like you, I trust very few people to work on my car, so when it came to the glass of course I did it myself. I used a combination of the two. I first set the glass in with butyl and then followed by backfilling it with urethane. Easy with a little help.

Mike
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post #3 of 137 (permalink) Old Mar 16th, 12, 8:45 AM
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Re: Butyl or urethane... AAARG!!!

The last several cars I have done I have used butyl for the same reasons you gave. One of my 69's has had the new windshield installed by me 15 years ago and is fine.
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post #4 of 137 (permalink) Old Mar 16th, 12, 8:57 AM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by Mike72ss View Post
Dave, I'm like you, I trust very few people to work on my car, so when it came to the glass of course I did it myself. I used a combination of the two. I first set the glass in with butyl and then followed by backfilling it with urethane. Easy with a little help.

Mike
Butyl and urethane are not compatible and combining them does not meet national glass installation standards.

Butyl was never used on these cars from the factory. Cruise night GM engineers without a degree pass that misinformation to other hobbiests.
The man in this link sells kits to do an installation the correct way. He also provides the installation service.
http://www.camaros.org/forum/index.php?topic=7255.0 And if you look at it it's an excellent job.

I've had glass installed using urethane for decades at the shop with no issues. Find a qualified glass tech to do it. Or buy a kit and do it yourself. It is illegal and unethical for a shop to use butyl.

More photos of the dam here: 69 front windshield molding

Last edited by Raven1; Mar 16th, 12 at 9:16 AM.
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post #5 of 137 (permalink) Old Mar 16th, 12, 9:14 AM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by Dave-1970 View Post
Never heard of a windshield dislodging from hard braking or a wreck???
There are videos of butyl installed windshields blowing out. Hard braking? That's really a stretch of reality.
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post #6 of 137 (permalink) Old Mar 16th, 12, 9:20 AM
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Re: Butyl or urethane... AAARG!!!

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Butyl was never used on these cars from the factory. Cruise night GM engineers without a degree pass that misinformation to other hobbiests.
Without name calling, I followed a respected member, Brain Martin's (MARTINSR) advise.

“Basics of Basics” Window setting
By Brian Martin

First let me say that the information in these instructions was compiled after years of installing and repairing rusty and leaking window pinch welds. I feel that with what I have seen in failed, overly rusty window pinch welds, and where I have seen pinch welds that have remained in good condition gave me a good idea on what works and doesn’t work. The rust found in window pinch welds is many times directly related to how a window was previously set. These instructions I feel give the best seal and long lasting results. Let me say that there are a few different ideas on things, these have worked very well for me. This instruction is starting after any rust repair, primer/paint. That would require MUCH more instructions.

First off get some 3M (or there are other brands) "pinch weld primer." It comes in a little 1/4 pint or so sized can and has a brush attached to the underside of the lid. Remember that you only apply this over a very clean surface. You should have a clean painted or primed pinch weld. The “pinch weld” is the area where the window butyl tape actually sits. If you will notice that is where you will see the spot welds that hold the inner and outer pieces of that area together. These pieces are STRSW (Squeeze Type Resistance Spot Welder) welded and “pinched” together by the welder, hints the name “Pinch weld”.

Before you install the clips be sure they are correct!!! You should start with either new ones or VERY nice old ones. When they are installed the top of the clip should be just a hair below the top of the pinch weld or body surface. I also recommend that you trial fit a piece of the molding to see if it fits correctly. This is time very well spent. If you find later that the clips are wrong, you will REALLY wish you did this trial fit.
You could even set the window in on some rubber blocks and install the moldings to be sure it will all work well.

The Butyl tape will not remain the advertised size when the window smashes it down. So don’t think that the ¼” butyl tape will STAY ¼”. That is why the tape you use is larger than the actual space you will have between the bottom of the glass and the top of the pinch weld surface. ¼” Butyl tape (3M is one brand, there are others) will end up at about 3/16, 5/32 or even down to 1/8”. The 5/16” will end up at about ¼ or 7/32”. The 3/8” will be 5/16 or 9/32”. The butyl tape can be flattened more, if you get it warm enough. So these numbers are used as a guide only.

After you install the clips brush the pinch weld primer on the bottom of the pinch weld where the butyl tape is going to lay. Brush up around the clips good. The paint gets scratched when you slip the clips on to the studs and this primer will help protect it.

Next you want to set the window in the hole and find what rubber setting blocks you want to use. There are a few that come with the butyl tape kit and you set them different ways to make them higher or lower. Be sure that the window fits evenly all the way around. Run a piece of masking tape from on the glass out onto the body on the sides and the center of the top and bottom. Really only one should be needed but it helps to have more so you helper can see one well too. These tapes are then cut on the edge of the glass so you can remove the window again. Just leave the tape on the window and the body for alignment purposes.

Be sure the window is clean and free of residue of any kind. With it lying on its back, put the butyl tape on the edge of the glass without hanging off. Roll it out and as you go you can pull the paper off it so that way when you come to a corner you can get around it. If the paper is on, you can't get around the corner. But you want the paper on as you are going down the tops and sides to help you get it straight and so you don't touch it. At the point where they meet, run one next to the other and at the point they pass, cut it with a NEW razor blade. Then DON'T touch the tape, using the razor push it, blending it together. Most guys will tell you to make this joint at a certain spot like on the side or at the bottom. I really don’t think it matters as far as leaking, if it is done incorrectly it WILL leak, what does it matter where it leaks? The point is, do it properly and it won’t leak. I like to look at where it will be the least seen. On the sides it is usually seen and looks like hell. I usually make this splice at the bottom; it seems to be the most hidden spot. You can get the butyl tape in ¼”, 5/16” and 3/8” in diameter. I have found that the 5/16” is the most common with ¼” being used in late model cars on the quarter windows. The 3/8” is rarely used and can really get you in trouble. If you set the glass with the 3/8” you may find that it is impossible to install the moldings because the glass is too high!

NOTE! Some of the new (and replacements for older cars) windshields are thinner glass and the 3/8" butyl tape is needed to set the glass. It raises the glass up to make up for this. So, check with a good trial fit first! If you have an original glass DO NOT use 3/8” butyl tape it will raise the window up too high and the moldings will not fit!

Then with your helper set the glass in using the masking tape as a guide. DON'T LET IT TOUCH until you have it where you want it. YOU WON'T HAVE A SECOND CHANCE the butyl tape sticks RIGHT NOW and will not let go. If you have the glass a little over or up or down too much you can move it a LITTLE after the glass is lying in. Before you push on the top of the glass, using a plastic setting tool or even a piece of wood you can wedge it into the pinch weld channel and pry the window over, VERY carefully. At this time it is best to get it warm. If you can get it in the sun and warm up the glass and butyl tape and push on the top of the glass to get a good seal all the way around.

Now comes the real important part, sealing. First let me say that I have done many windows and used NO sealer what so ever. The Butyl tape alone should be sealing enough. But as an added "safety net" I do the following.

I take a plastic "bondo" spreader and cut it to about a half inch in width. I also round the corners with the razor nice and clean. Using a high quality urethane sealant I put a little strip right on the side of the glass edge or on the butyl tape it's self. Using the spreader I spread it down the side of the glass over the butyl tape to the bottom of the pinch weld, forming a seal from the top to the bottom vertically. In other words this sealer is covering the edge of the glass and the butyl tape, THAT IS IT. The sealer goes down to hit the bottom of the pinch weld right where the butyl tape is resting, but that is it. That bottom edge of the sealer where it hits the pinch weld is most critical. Be sure that it IS sealing down at the pinch weld. It should have a nice clean line as it hits the pinch weld. If it pulls up off the pinch weld, it is not a seal. Don’t assume because you have that sealer down in there, that it is sealed. If you put the bead of sealer in there and then spread it with the bondo spreader with pressure against the edge of the glass and butyl tape, it WILL flow down and seal the bottom, you just have to be sure you are doing that. DO NOT PUT THE SEALER ALL OVER THE CLIPS OR FILL THE CHANNEL this is a DEATH sentence to you job. When you are done, you should be able to still remove the clips if you wanted, that is doing the job right, no sloppy sealer all over the place just because the molding will cover it. Every little nook and cranny created by the sloppy sealer is a place where water will gather and sit longer than needed. This is a place for rust to start.

If you do this and you and see the seal has been made from the top edge of the glass down to the bottom, you know it will never leak. When water gets in there, it will be able to evaporate. If you fill the channel with sealant, the water gets in and can't get out!

You now can put the moldings on and off at your leisure. If your molding is giving you trouble and not clicking into place on the clip. You can take a rubber squeegee and place it on top of the molding and then a small block of wood and tap; JUST tap lightly on top and you can get even the most stubborn molding on. But if you trial fit them and didn't put sealant all over them this shouldn't be needed.

Note: These suggestions are for full frame cars, vintage cars. Most every late model car was designed to have the stationary glass “urethane” set, DO NOT use butyl tape on a uni-body late model car. The glass is a part of the structural design of the car. Using butyl tape could jeopardize the structural integrity of the safety features in the vehicle. You can in fact use the superior urethane setting technique on any car if you choose. However, it makes things a lot harder. A late model cars window seal can’t be seen. So a sloppy urethane job is hidden. On a 68 Camaro for instance, you SEE the windshield sealant from the inside of the car. So to use a urethane needs a real pro to apply. Applying a bead of urethane that is perfect all the way around the window is next to impossible, most pros don’t even get close. They don’t have to get good at it, 99.9 % of the cars they are doing are late model where it is completely hidden. So you would need to use a foam tape “dam” along the sides and bottom of the glass at the very least. This “dam” holds the urethane from “oozing” out into the passenger compartment.
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post #7 of 137 (permalink) Old Mar 16th, 12, 9:45 AM
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Re: Butyl or urethane... AAARG!!!

I don't care what Brian says. If he wants to use butyl and suggest it that's his right. Although he is in the business perhaps even he does not know the history of windshield installation. It's my opinion a pro should not recommend the use of butyl. Although butyl and urethane are used together by some, they are not compatible.

Below from John Hinckley. If you don't know who he is, here's a little info. http://www.corvettemuseum.org/librar...hinckley.shtml

John Hinckley: "GM never used butyl tape or anything like it to install windshields or backlites. Period.

The body opening flange was coated with black silane primer using a flow-brush 30 minutes prior to installing the glass, and all the reveal molding clips were installed to the Body Shop-installed weld studs.

The glass was placed on a powered rotating fixture, inside edge up, retained by suction cups.

The glass periphery was cleaned using a solvent, dried, and a different silane primer was applied.

A fabric-reinforced self-adhesive foam rubber "dam" was extruded and applied to the glass just inboard of where the Thiokol adhesive would later be applied; the purpose of the "dam" was to contain any Thiokol "squeeze-out" so it wouldn't show from the inside past the edges of the interior garnish moldings after the glass was installed to the body.

After dam application, pumpable Thiokol adhesive (with a pyramid-shaped cross-section created by the dispensing tip) was applied adjacent to the dam, all the way around the glass.

Lower glass supports were fixture-located and screwed to the cowl, and rubber spacer blocks were glued to the opening flange. The spacer blocks set the height of the glass relative to the body to ensure a good fit of the reveal moldings.

The prepared windshield was removed from the rotating fixture, installed in the body opening, and pressed down against the rubber spacer blocks; wooden tonque depressors were used to "paddle" the Thiokol around the edges at a 45* angle from the top edge of the glass to the bottom edge of the body opening to ensure a continuous seal all the way around the glass.

Reveal moldings were installed.

That was the plant production process, and explains what is sometimes described as a "rope" being found when an original windshield is removed - the "rope" is the fabric-reinforced rubber "dam" that was applied prior to applying the Thiokol adhesive.

If you'll look in Section 4 ("Fixed Glass") in the Fisher Body Service Manual, you'll see exactly the same process for windshield replacement, except the "dam" wasn't included with the Service kit - masking tape was used instead to control "squeeze-out".

The Thiokol installation passed the Federal MVSS windshield retention tests, and contributed substantially to the body's torsional stiffness; it also helped the structure pass the roof crush test. It's illegal to replace a windshield with butyl tape, although some glass shops do it as a less-expensive short-cut method instead of doing the job right."

Last edited by Raven1; Mar 16th, 12 at 10:27 AM.
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post #8 of 137 (permalink) Old Mar 16th, 12, 11:06 AM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
I don't care what Brian says. If he wants to use butyl and suggest it that's his right. Although he is in the business perhaps even he does not know the history of windshield installation. It's my opinion a pro should not recommend the use of butyl. Although butyl and urethane are used together by some, they are not compatible.

Below from John Hinckley. If you don't know who he is, here's a little info. http://www.corvettemuseum.org/librar...hinckley.shtml

John Hinckley: "GM never used butyl tape or anything like it to install windshields or backlites. Period.

The body opening flange was coated with black silane primer using a flow-brush 30 minutes prior to installing the glass, and all the reveal molding clips were installed to the Body Shop-installed weld studs.

The glass was placed on a powered rotating fixture, inside edge up, retained by suction cups.

The glass periphery was cleaned using a solvent, dried, and a different silane primer was applied.

A fabric-reinforced self-adhesive foam rubber "dam" was extruded and applied to the glass just inboard of where the Thiokol adhesive would later be applied; the purpose of the "dam" was to contain any Thiokol "squeeze-out" so it wouldn't show from the inside past the edges of the interior garnish moldings after the glass was installed to the body.

After dam application, pumpable Thiokol adhesive (with a pyramid-shaped cross-section created by the dispensing tip) was applied adjacent to the dam, all the way around the glass.

Lower glass supports were fixture-located and screwed to the cowl, and rubber spacer blocks were glued to the opening flange. The spacer blocks set the height of the glass relative to the body to ensure a good fit of the reveal moldings.

The prepared windshield was removed from the rotating fixture, installed in the body opening, and pressed down against the rubber spacer blocks; wooden tonque depressors were used to "paddle" the Thiokol around the edges at a 45* angle from the top edge of the glass to the bottom edge of the body opening to ensure a continuous seal all the way around the glass.

Reveal moldings were installed.

That was the plant production process, and explains what is sometimes described as a "rope" being found when an original windshield is removed - the "rope" is the fabric-reinforced rubber "dam" that was applied prior to applying the Thiokol adhesive.

If you'll look in Section 4 ("Fixed Glass") in the Fisher Body Service Manual, you'll see exactly the same process for windshield replacement, except the "dam" wasn't included with the Service kit - masking tape was used instead to control "squeeze-out".

The Thiokol installation passed the Federal MVSS windshield retention tests, and contributed substantially to the body's torsional stiffness; it also helped the structure pass the roof crush test. It's illegal to replace a windshield with butyl tape, although some glass shops do it as a less-expensive short-cut method instead of doing the job right."
I just had a windshield installed by a professional and basically he did the same exact procedure. Installed a little 3/8" adhesive tape around leaving about 3/8" for urethene. Let is sit about 2 minutes and set in place. The trim snapping onto the body weld studs sets the glass to the required height. The little dam keeps the urethane from "squishing" out. He also stated that this windshield is an "integral part of the body and intended to help keep people inside the car should a roll over occur and should NEVER be set with butyl tape". His words, not mine.

Later,
Wayne
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post #9 of 137 (permalink) Old Mar 16th, 12, 12:17 PM
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Wink Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Raven1 View Post
Below from John Hinckley. If you don't know who he is, here's a little info.
Isn't he the guy who shot Reagan??
BillL

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post #10 of 137 (permalink) Old Mar 16th, 12, 12:31 PM
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Re: Butyl or urethane... AAARG!!!

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Originally Posted by Ark68SS View Post
Isn't he the guy who shot Reagan??
BillL
I never heard that before, and I'm sure John never heard it either.
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post #11 of 137 (permalink) Old Mar 16th, 12, 4:46 PM
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Wink Re: Butyl or urethane... AAARG!!!

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I never heard that before, and I'm sure John never heard it either.
I bet he has. The guy's kinda famous.
http://en.wikipedia.org/wiki/John_Hinckley,_Jr.
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post #12 of 137 (permalink) Old Mar 16th, 12, 5:09 PM
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Re: Butyl or urethane... AAARG!!!

Quote:
Originally Posted by Ark68SS View Post
I bet he has. The guy's kinda famous.
http://en.wikipedia.org/wiki/John_Hinckley,_Jr.
BillL
I was joking.
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post #13 of 137 (permalink) Old Mar 16th, 12, 6:04 PM
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Re: Butyl or urethane... AAARG!!!

OK, kidding aside...

Based on what has been posted, there are kits available to correctly install a window like the factory did back in the day. Looked up the "First Calss AUto GLass" company shown on the side of the van in the Camaro link and their site is down. I'll try to call later.

However, if they are unreachable, who else sells these kits, or the appropriate foam dam material to correctly mount a windshield? Anyone in Southern California know of a supplier? Based on the pics, this stuff is available from someplace.

I have always used butyl tape because that is what was used by the local glass shops and what was available. never had a problem with windows popping out, but never rolled my car either. Hated it because it always remained sticky and messy, but that was all I could find. Did have a window not stay in place when glued in with urethane, tho.

PLease, someone help me do it right and find the correct materials, I am sure I am not the only one in need of this info.

Thank you,
Tom

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post #14 of 137 (permalink) Old Mar 16th, 12, 6:50 PM
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Re: Butyl or urethane... AAARG!!!

^^^^^Send Jeff a PM on CRG. I've referred people to him and they contacted him. If your urethane failed it was done wrong. I installed my first windshield using it in 1985 and had no issues.
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post #15 of 137 (permalink) Old Mar 16th, 12, 9:52 PM
 
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Re: Butyl or urethane... AAARG!!!

The last several cars I have done I have used butyl for the same reasons you gave. One of my 69's has had the new windshield installed by me 15 years ago and is fine.
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