Do-it-yourself window glazing is one of those tasks that is not very difficult to do, if you do it correctly. The satisfaction of glazing a window yourself, saving money and knowing that it has been a job well done is well worth the time and the effort.
The right tools are essential for glazing windows. If there is old, worn, cracked or chipped glazing on the window, it needs to be removed. Using a heat gun will soften the old glaze. A putty knife can then be used to just pry it off and away from glass. Smooth the frame bed for the glass by sanding or scraping away any left over glazing compound or old paint residue with a sanding block or folded up sandpaper to reach into the corners.
Types of glaze
There are two types of glazing on the market, oil-based and latex-based. Latex is easier to work with and is a good choice; but if you need a very professional, smooth-looking glaze, oil works best for this.
Latex glaze is soft right out of the tube and can be literally "caulked" right on. But oil-based putty is a bit different. It is a harder compound that will come in a container, and although it can be used as it is, here is a tip to make it easier to work with.
Oil-based glaze can be heated up in hot water while still in the container to make it much easier to work with when putting it on the glass and frame. Warmed up like this, it becomes very pliable and almost has the consistency of children's play type dough.
Priming and preparation
Prime the wooden frame where the glass will sit. A great primer is regular linseed oil, which can be brushed on just as if it were paint. This will keep your glazing putty pliable and will prevent cracking for years to come.
Before putting the glass into the frame, always put a small bead of either latex caulk or oil-based glaze on the frame bed. It doesn't have to be spread out, but it does have to be one continuous solid bead.
Safety first when laying glass. ALWAYS wear gloves when doing this. Glass edges are sharp, and even common garden gloves will prevent a nasty cut from happening.
After your framing bead has been put down on the frame bed, press the new window glass down into it. Wiggle it a bit to set it in solid and trim or wipe off the excess. This will give a solid base as well as weatherproof the glass so that air and water won't penetrate.
Then, just dig out a small ball full of putty and roll it into pencil- or snake-like lengths. If the oil-based putty has been warmed up ahead of time, it will be easy to roll. Press the "pencil" into the frame and onto the glass. Smooth it out with a putty knife, pushing it into the frame. This may take a bit of practice to make it work, but the results will be worth it.
Drying and painting
Latex glaze will skin over fast but the underneath remain very soft for hours. It is best to let the latex harden a bit overnight before painting and installing the frame back into the window.
Oil glaze putty will never truly harden and will remain pliable for years. The frame can literally be painted and then reinstalled as soon as it is finished. Be careful not to push on the glaze when doing this because at best you'll leave a fingerprint or two, but at worst, you may leave a big dent or a gouge in the putty.