When glazing old windows there are a few things that can make your project go smoother and look like a professional job. Glazing is not something that is learned in a day, it does take some time to get the clean, crisp glazing lines that a seasoned glazier can consistently produce, but with a little practice and by utilizing these five secrets you can make huge strides toward a quality glazing job.
One great thing about putty glazing a window is that unlike painting or most other window restoration tasks it can easily be scraped off and redone without any consequences. Glazing putty can be worked and reworked until you are satisfied and you don’t have to go back and start over or sand off paint.
Below I’ll tell you five ways you make your window glazing so perfect no one will ever know you’re a beginner. Let’s get started!
1. Choose the Right Putty
Choosing the right glazing putty can make your job so much easier. And likewise choosing the wrong putty can make the task seem nigh on impossible. I have seen many people foiled by using a bad glazing putty. I have written a whole post on choosing the right glazing putty so check that out before you buy any putty, but let’s walk through some of the basics here.
Choose the right putty for the right window. Steel and Aluminum windows require a different putty than wood windows. Glazing window in place requires one kind of putty versus glazing them in the garage or shop. And then there is the stuff most people try to glaze windows with that is actually one of the hardest putties to work with, DAP33. Stay away from it at all costs. It’s gooey, difficult to work with, and takes a long time to cure.
Here are my go to choices for glazing putty:
- Wood Sash in Shop Only – Austin’s Glazier’s Putty or Sarco Type M
- Wood Sash in Place – Austin’s Glazier’s Putty or Sarco Dual Glaze
- Steel Sash – Sarco Dual Glaze
- Mildew Prone Areas – Austin’s Glazier’s Putty
2. Only Use Fresh Putty
Glazing putty has a relatively short shelf-life. If your putty has been sitting around for more than 3-4 months it’s time to get some fresh putty. The oils in glazing putty separate over time and you’ll need to keep it mixed. Storing putty in the freezer can extend it’s life greatly to a year or so.
When you open a fresh pail of putty there will often times be a skin of cured putty on the surface. DO NOT mix this back into the putty. This is a sacrificial layer that must be scraped off and disposed of. If you mix this back into the putty you will have chunks that do not dissolve no matter how much you mix and that will yield a clumpy mess of a glazing job.
If your putty feels too dry then you can mix in a little bit of RAW linseed oil (not boiled linseed oil, raw). Mix it throughly until you get the consistency that you want. Kind of like a slightly sticky PlayDough feel. If it’s too oily then add some whiting to the putty until you achieve the desired mix. You can keep adding either of these materials to get the right mix.
3. Use a Firm Putty Knife
This one is personal preference but most window professionals I talk to use a firm putty knife for glazing windows. You have more control and can smooth out inconsistencies in the glazing rabbets better. A firm putty knife gives you firm, even pressure all the way across which means a consistent line of glazing putty.
Finish glazing a window requires a decent amount of pressure to make sure the putty is packed in tightly which creates that nice tight seal for your window glass.
4. Clean the Glass Immediately
Glazing a window always results in some of the oil from the putty getting on the glass. This needs to be cleaned before painting and there are several ways to do it, but one of them is better than the rest and it’s called whiting.
As soon as you are finished glazing a sash use an old paint brush or chip brush to brush a liberal amount of whiting powder (chalk dust) onto the glass and putty. The whiting will carry away the oils and clean the glass as well as absorb the residual oils from the glazing putty to help expedite the curing process.
The trick is, DON’T WAIT! Every minute that you wait to clean your glass the oil is drying a little bit more requiring more and more scrubbing until eventually the oil can’t be cleaned off the glass with anything but a razor blade. As soon as you finish glazing a sash, clean it with whiting and then set it aside to cure.
5. Make Smaller Lines
I see too many people, even on my own crew, glaze window after window and then at the end of the day try to clean the oils off. It takes twice as long and requires way more effort. Work smarter, not harder and clean it quickly.
Nothing looks more amateur with window glazing then looking through from the inside and seeing the backside of the putty. You’re glazing putty should be invisible from the inside on the window. To do that you need to make smaller lines than you think.
I try to set my putty lines back behind the glazing rabbet about 1/16” to 1/8”. That gives me a space for imperfections and also allows me to run a paint line over top of my putty and not have the paint show from the inside either. Clean, crisp interior lines really show off your skills and will convince people of your pro status.
Glaze a line and then check it from the inside. If you see putty then take another pass until you get the line back to the 1/16” to 1/8” range.
There are a lot of resources on my site about window glazing that can feel free to search through. I also have my own teachable course called DIY Window Restoration that will walk you through the entire window restoration process from start to finish. You can learn more about the course right here!
Founder & Editor-in-Chief
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
6 thoughts on “5 Secrets to Glazing Windows”
We are using Type M on some 100 year old windows. Getting some pull or tear marks at glass edge, any tips to keep this from happening
I used Dap latex in the tube window glazing . It is water based. 3 stories up to find out it is junk…from reviews. Are you aware of this product? I do not intend on doing this again in a few years. Do you think it is reasonable to keep it? And how much of it needs to be removed to use the good window glazing. Sarah
Wow… I am a stainglass restorer; i learned from her. Exceptionnal. For a strange reason, the best artisans i have met are… women. More precise/consciencieuse.
Thanks again Scott for your efforts in teaching us these tips and tricks. When I’m ready to start my windows, I will be back to get the supplies from you!
Thanks for the tips!! I could use your advice about my windows. I bought a 100 yr old house in March 2020, just before my governor shut down the state. (Yes, it’s THAT woman from Michigan.) LOL.
I wish I had found your blog before I started. I still can’t live in my house!!!
I think I made a mistake last summer. The window in the garage faces west and had never been repainted or replaced. Yes, most of the paint was off it and it didn’t take a lot of work to scrape off what was left. I sanded a little, cleaned, and then primed and painted the whole thing. But I haven’t glazed the panes yet.
I realized after I was done that that was a mistake.
Do I have to strip the paint off where the glazing will go or can I just glaze over it? I don’t know where else to get this info. Thanks for any help u can give. Just call me . . .
Tired in Michigan