Glazing over

Over the past few weeks I've slowly started the process of reglazing the sashes in the old double-hung windows on the West and South side of the house. At some point most of the windows on the North and East had been replaced by vinyl replacements, but the rest were never touched and they show it. Several have broken glass – those I'm tackling first – but the rest just need to be scraped, reglazed and painted. I've only done three so far, but I figured I'll share the small amount I've learned from the endeavor.

Here's the start of sash number three with the glass removed. I recommend removing the sash from the frame if possible. It makes the project much easier.

It's absolutely essential to get all the old glazing out of the rabbit in order to get a good final product. I've found that a heat gun and a glazier's tool works wonders, but use caution: Heat will break the glass. If you are re-using the glass, you'll need to shield it with some old aluminum flashing or some aluminum foil. Likewise, if you're replacing one pane of a multi-pane window, you'll need to shield any adjoining, undamaged panes while you're removing the glazing. If you're simply replacing the glass, wrap the old pane in a cloth, tap it gently with a hammer and remove it prior to starting. It'll make life easier.

While you're scraping, make sure to remove all the old glazier's points from the wood. They should be located every six or eight inches around the perimeter of the glass. If you intend on reusing the glass, be careful removing the glazier's points – it's very tricky. My windows had simple flat triangles rather than the kind with vertical tabs and they were nearly impossible to grab. I've found that by taking the tip of the glazier's tool, laying it flat against the glass with the tip just behind the edge of the glazier's point and spinning it while pulling gently away from the sash I can get it removed.

After you've removed the glazing and points, scrape any old paint off the rest of the sash, sand it and give it a good coat of primer, including in the rabbit. I gave each sash two coats of primer before I started the glazing.

Next, fill the bottom of the rabbit with a ¼ inch or so of glazing. I prefer the glazing putty that comes in a tub. I used the stuff in a tube on the first window repair and I dislike it – it dries too quickly, is hard to tool and doesn't seem to make a great seal. To fill the rabbit I put some putty on a glazier's tool and simply push it along the rabbit. There's no need to be neat in this step. Once you have a good bead all around the sash, place the glass in the rabbit and gently push around the entire edge. This should give you a good seal with about 1/8 inch of putty. You'll scrape the excess up later.

Take your glazier's points, lay them on the glass, and using a putty knife carefully press them straight into the sash while applying a modest amount of downward pressure. On the first window I was a bit too heavy handed and ended up cracking the pane.

Take a golf-ball sized piece of putty and work it in your hands to soften it, then roll it out to form a rope – about 3/8 inch – and place it around the perimeter of the pane.

Once you've placed the putty, take a flexible 1 ½ inch putty knife, place it at a 45 degree angle between the sash and the pane, and draw it slowly and smoothly along the pane while applying even pressure. Make sure the putty has a good seal on both the pane and the sash. Carefully remove the excess putty once you've completed the side. Continue with the remaining sides, carefully smoothing the corners into a nice groove. I've found that by turning the putty knife out and up as I'm approaching the corner, I can create a nice groove.

The putty dries slow, so wait a week before painting the sash. I'm hardly an expert, so if anyone has any additional tips or corrections feel free to share.