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Glaze or caulk windows?...

Stickley's picture

I'm re-doing some old wood windows and got very frustrated with the 2 week cure time recommended for glazing before painting. Plus, it doesn't stick to the wood that tightly. I talked with one knowledgeable person about just using a good caulk instead of glazing and he said "try it." Can't I can get just as good protection and sealing from caulk for the next 15 years?  (I live in a hot climate and it never freezes here, if that makes any difference)


(post #60922, reply #1 of 17)

I once watched  a professional use polyurethane caulk to reglaze wooden windows in an old foundry that was getting a facelift. Used a licked, wet finger to smooth the joint -- wonder if he's still around after that. As far as the caulk goes, it hasn't failed in ten years. This was a Tremco product, Dymonic, which is a bit pricey, but PL or GE is available for less. Can be tricky to use, since it sticks to anything (fingers, clothes, rags, etc.), but it retains its elasticity for a long time, a good trait for window glazing.

(post #60922, reply #2 of 17)

My father always used the expression "he doesn't know s*&t from putty; I'm surprised his windows don't fall out...."

(post #60922, reply #3 of 17)

Glazing points keep the pane in, not the sealing compound.

(post #60922, reply #4 of 17)

Properly applied standard window glazing should last twenty years or more…..easily. Prime your bare wood and the edge of the glass with a bit of boiled linseed oil immediately prior to applying the glazing. Wait maybe four days or so before painting (in warm environment or temps)………….until the glaze has skinned over and has a reasonably dry and slightly firm surface. Then prime with an oil-based primer. Let dry for a day. Topcoat of your choice, oil or latex. SarcoSeal or Dap33 are reliable glazes. I've never waited two weeks. By then the glazing can be too dry and essential moisture is lost and that dramatically shortens the life expectancy because curing of the glazing takes place too rapidly. I've seen others do this and seen the short-lived results.

I'll admit to running an experiment with polyurethane caulk instead of glazing, out of curiosity. Just stuck the new windows in place recently. These are simple single-glazed windows on an outbuilding over at the family farm.

If you decide to try the poly caulk (the only type I'd even consider using)………here's what I found for getting a neat job with this material. In your case, make sure your glass is clean and your wood free of anything crumbly or dusty. Then apply masking tape to the glass along the appropriate line to prevent making a huge unmanageable mess on the glass. I'd recommend 1 ½". Do this carefully, getting the lines straight and the corners right. Then fill the area to hold the caulk amply, as you would with standard glazing. Next, strike off the caulking with a glazing knife just as you would standard glazing compound. This means one clean swipe from corner to corner. Remove the excess from your knife with a paper towel. A little mineral spirits is in order. The excess that gets squeezed up on the surface of the window frame is easy enough to slice off and reuse in the next run. The excess that squirts onto the masking tape should probably be disregarded unless it's an awful lot of it. You might end up smearing it onto the glass if you go after it.

If you're talented with the knife on standard glazing compound, you shouldn't have much trouble getting the hang of this. But, it takes considerably longer all in all to get the window glazed with the caulking. Wait a couple of days for the caulk to firm up and then run a utility knife down the glass side edge of the caulk to cut the tape, in case any of it is under the caulk. Then pull the tape off. You should now have a bead that's more or less indistinguishable from standard compound and ready for paint.

If you try to just fill the void directly from the gun, I pretty darn sure you'll have an irregular looking result that you won't be pleased with at all. Very hard to control and get a professional looking result And using fingers for tooling always looks that way. Concave result, not flat and true.

More work and hassle? Yup. Is it worth it? I'll let ya know when I see what the life of it is. I really doubt it'll out perform the standard glazing, but we'll see. That's what experiments are for. <G>

Knowledge is power, but only if applied in a timely fashion.

Knowledge is power, but only if applied in a timely fashion.

(post #60922, reply #5 of 17)

For 20 + years part of the services we offered in our "mom & pop" lumberyard was window repair.  I hated to see a "caulked" in glass sash come in the door for repair.

Polyurethane, construction adhesive, gutter seal, and other sealastic caulks were always a battle to remove. 

Where as the tried and true Dap 33 glazing compound made the job do-able.

But then how many broken windows does a normal house have your lifetime?

And how many homeowners  correctly fix their own windows?

..............Iron Helix

.......Iron Helix

(post #60922, reply #6 of 17)

Have only 20 9-over-9 double-hungs left to go in my house that were caulked with every type of caulking you mentioned, including the adhesive type, and all of it very poorly done.  2 are finished, including some other repairs as well.  Some of it was over old glazing compound.  Definitely would not want to do this for someone else at any price.


(post #60922, reply #9 of 17)

great advice..a plastic spoon is indispensible too..BTDT..lick it first..


Spheramid Enterprises Architectural Woodworks

Repairs, Remodeling, Restorations.   

(post #60922, reply #10 of 17)

Thanks to all who offered advice. I had never heard of polyurethane caulk and was actually thinking of using a 35 year latex or 50 year "Elastomeric". My thinking was that it goes on much easier (from a gun; no need to form rolls of product like you would with glaze; easy to take out later, etc. ). I had a couple windows glazed at a glass shop and found that the glazing pulled away from the wood in a few places by the time I got home. NOT the professional and long lasting job I was looking for, thus I started thinking about alternatives. I will try again with glazing myself, making sure to clean the wood well first.  Maybe do a panel or two with caulks, just to test.




(post #60922, reply #11 of 17)

Oh my. Not again!

No need to make snakes of the stuff. Complete waste of time. Period. Amateurish approach.

After applying a film of BLO to the area, take a handful of the stuff and knead it a bit. Then with the wad in your left hand (assuming you're right handed) just start wiping wads of it off your fingers into the glaze area. Place another along side that wad, etc. until you've packed the entire length of the run. You want to be overfilled at this point. Take your knife and with the flat side, pack the matrial a bit into the corner. Now it's time to do the swipe......from corner to corner. One continuous swipe. This is done with the axis of the blade parallel to the length of the corner. Angles and pressure critical. More pressure than you might suspect.

Knife must lay/tilt from wood edge to glass so that the cut leaves the right amount on the glass (enough so that it totally fills the corner, but can't be seen from the inside of the window) Elevation angle of knife is also highly critical. The material will let you know when you've got the right angle because the material will cut and lay perfectly behind the knife blade. Too high of an angle and you've got trouble, too low and you've got trouble. Twist wrist a bit upward and away to exit corner on a "miter" when you get there. Just watch the cutting edge of the blade and it'll guide your manuever as you exit these corners. Now go back and pick up the excess that that got cut away. Knead it back into the wad in your hand and begin the next side.

Once you get one of these right and the magic perfect run of glaze appears behind the tip of your knife, you'll have a smile. It's like learning to ride a bike. Once you've got it down, your hand will never forget what to do.

Don't worry about any BLO or glazing smears that get on the glass as they'll clean up easily with a razor knife and some Windex after your final topcoat is dry. Just don't poke under the edge of the new glazing with that razor knife or you just spoiled the very valuable seal.

If the glazing was falling out on the way need to find a diffferent glass shop, me thinks. Sounds absolutely ridiculous from here.

If you have any trouble getting the hang of all this, just bring a window over to my shop and I'll show you how. You'll be doing this well in 20 minutes time. <G>

Knowledge is power, but only if applied in a timely fashion.

Knowledge is power, but only if applied in a timely fashion.

(post #60922, reply #12 of 17)

One of the purpose of glazing is to shed water. Caulk smeared in, in an uneven fashion won't do that and could shorten the lifespan of wooden windows.

Expert since 10 am.

(post #60922, reply #13 of 17)

Actually the glazing compound is the "fill" to the watershed between the glass and wood sash,  The final paint primer and finish coats should seal the line of the glass to the gazing compound.  So a good paint with a lap to the glass is the waterproofer.

I have had people return the repaired sash after a time exposed to the elements, but never painted, and complain that our glazing work "leaked". Education followed.

The second bad error in glaze compound application is to allow the height of the glazing compound to rise above the elevation of the bottom rail glazing rabbet. I closely monitored my new shop employees for this leak prone error.

In those circumstance any water running down the exterior of the glass that would meet an opening/crack in the painted glazing compound and glass interface will be capillaried into the glazing rail and then leak to the inside if the sash.

Too much is as bad as too little.  If you can see the back side of the glazing compound bead from the inside of the sash, then you may have used too much glazing coompound.

I also found that WD-40 applied to dry wood rails would do about the same as Boiled Linseed Oil (BLO).......and with only a small wait before applying Dap33.

Goldhiller's description of kneading the Dap33 is important in that it remixes the material and warms the materials to help produce adhesion and a smooth flow when tooling the finish glazed lite and sash.  Nice job, Mr. Goldhiller!

....................Iron Helix

.......Iron Helix

(post #60922, reply #14 of 17)

Good tips and explanations of the "why" of them.

You do realize that we haven't begun explaining bedding of the glass? That might take many words. Too many.

There used to be a very excellent page available with photos and explanations of the entire process. Really good. Unfortunately, it isn't available anymore.

As for me, I'd also advise everyone to leave the spoon in the drawer and to use a regulation straight-bladed knife. Reason being that a concave surface naturally leaves thin edges on the glaze, like a hollow ground knife. These thin edges are much more prone to drying out and losing their ability to maintain the seal necessary to a long-lived glazing. Sorry, Sphere....ain't pickin' on ya.....I'm just convinced this is a bad idea. :-)

I got a roar when about 6 years ago, I watched a Martha Stewart show in which she attempts to educate her audience about how to properly glaze a window. There she is, instructing everyone how to roll "the snake". Both me and the DW are screaming at the tube. LOL DW is an experienced glazier after we restored this Vic. Even she knew better than to swaller that crap. The glazing doesn't care if its rolled into a snake before it's stuffed into a triangular corner shape. The point of that would be...........???????? If you just knead the compound and pack it with the knife, the deed is done.

WD-40? Have you noticed any difference between the life expectancy using that instead of BLO? I've always conjectured that the BLO acts similar to a glue which fortifies the adhesion and acts as a sealer. I do know tht he life expectancy is greatly increased when it's used as to when it isn't. Wouldn't think that WD-40 would offer that potential advantage.

Knowledge is power, but only if applied in a timely fashion.

Edited 4/21/2004 10:29 pm ET by GOLDHILLER

Edited 4/21/2004 10:33 pm ET by GOLDHILLER

Knowledge is power, but only if applied in a timely fashion.

(post #60922, reply #15 of 17)

>> Wouldn't think that WD-40 would offer that potential advantage.

Don't know why not. WD-40 is a hardening oil, much like BLO. The volatile part evaporates fairly quickly, and the residue eventually gets sticky, just like linseed oil.

(post #60922, reply #16 of 17)

I would have to agree with the BLO as the premium choice....especially since BLO is the base for the Dap33 glazing compound.   

WD-40 was an answer to a shop situation where time of repair and employee friendly materials was essential to giving our customer that very short (1-4 hr) turn=around on a sash repair/reglaze.

Wd-40 does a good job of "wetting" the parched sash rail to allow for easier glazing and less pull-out.  Yes it mostly evaporates and probably has less ultimate binding power than BLO. 

But as the storm clouds roll in, and I'm 20 feet up on the second story window that the the neighbor kid's baseball selected as a point of impact....I'm quite happy to expidite the repair with a 2oz WD-40 aerosol.

...................Iron Helix

.......Iron Helix

(post #60922, reply #7 of 17)

Iron Helix and RVillaume have brought up a very important consideration. Subsequent repair and maintenance. I shoulda mentioned that too, but didn't. Much swearing to be heard at time of removal. I'm confident of that. That's why I used plexi for the panes in these windows so as to reduce the chances of breakage and need of a fix.

And I fear that once the PU caulk (or any other) is used to set the glass, it'll be a hell of a job trying to get the wood cleaned up enough again to provide a clean surface so that standard compound can adhere. I wouldn't want the job myself. I think this may well be a near irreversible committment. Once you start with caulk, you gotta continue to use caulk on that sash or spend more time than the window is worth if you want to return to glazing.

Although I did this to these barn sashes, I wouldn't really think of doing it on any house windows. Not at this time anyway. I think the folks who turn to caulk for their house windows are the same folks who never learned how to glaze a window or how to handle the knife. They think it's hard to do, but it isn't at all. I can glaze a window with standard glazing compound in 1/4th the time it took to do the caulk.

The reason I decided to try the PU is that like on many barn sash, the bead of glazing on these is much smaller than "standard" size beads (because the sash are made from thinner stock) and consequently that substantially shortens the life of the glazing. It dries out that much sooner. I'm hoping to reduce the maintenance time on these buildings over the long haul by using the PU. Maybe, maybe not.

These are simple barn sash (four lights each)and the fact of the matter is that I can currently buy new sash with glass for most of the holes in those various outbuildings for between $28 - $36. Still need primer and paint though. For that price, a guy really can't afford to fool around with repairs if very much is needed. But.....I put in the effort on four of these windows just because I'm the curious sort.

If you're having trouble getting the standard compound to stick tightly to your sash, I'm thinking that it may be because you aren't packing it into the window with the knife prior to cutting it, your wood surface isn't quite clean enough or you aren't using any BLO. Have you watched the folks at the local glass shop glaze a window? Much to be learned by simply watching the technique a few times. The attack angle of knife and pressure are both critical if you're to get a clean cut that doesn't leave the glaze wanting to cling to your knife, getting pulled back out again behind the blade. And so is the surface of that knife. It has to be gleaming clean. If yours isn't, some #0000 steel wool should help you get it there. Or buy a new one. I like the knives with the offset angle in the blade much better than a straight knife.

Knowledge is power, but only if applied in a timely fashion.

Knowledge is power, but only if applied in a timely fashion.

(post #60922, reply #8 of 17)

I did the usual contractor thing.  Sure! I can do that.  Reglazing 17 windows with 12-15 panes each.  Use boiled linseed oil the day before, after window 9, with a good flexible putty knife you will be amazingly fast at it.  Made good money once I got the technique down.  DanT

waterproofing--re: IronHelix's reply (post #60922, reply #17 of 17)

"Actually the glazing compound is the "fill" to the watershed between the glass and wood sash,  The final paint primer and finish coats should seal the line of the glass to the gazing compound.  So a good paint with a lap to the glass is the waterproofer."

In my experience, caulk retains its waterproof seal longer than paint, which would seem to make (properly applied) caulk a better choice.