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Re: Sash Glazing & Painting (with Video)

Posted: Sun Nov 29, 2015 4:49 pm
by johnleeke
I continue to prime the putty on most of my work.
I've got three side-by-side comparative field tests that demonstrate a longer service life with priming on the putty. The tests are in place 14, 15 and 19 years, with some sash that had primer and some that did not. Two are with Type M, one is with Glazol. On these three tests more than half of the sashes with no primer were ready for a round of spot paint maintenance because the paint seal with the glass had failed. The primed putty had no failures and needed no maintenance. This demonstrates to me that it is worth priming the putty if the people I work for want 5+ to 8+ years of longer service life before maintenance is needed.
I let the people I work for decide if they want to pay slightly more for a longer service life, usually it's about $5-10/sash more. Last year, all 23 people I worked for decided for longer service life. This year I've had 2 out of 18 decide not to, they were both DIY-type homeowners who figured they would be happy doing spot paint maintenance whenever it was needed. Homeowners and institutions that hire everything done almost always go for the longer service life.

Spacer Blocks update

Posted: Fri Oct 28, 2016 3:25 pm
by johnleeke
Spacer Blocks
Panes wider than 24” may require spacer blocks. Spacer blocks are needed around larger panes because they are heavier and may shift position, disturbing the putty before it has firmed up, resulting in wrinkles or tears in the painted surface of the putty. They can also be useful on smaller panes when the sash will get a lot of handling or transport that would shift the position of the pane. These little blocks are about the thickness of the pane and an inch or so long. They might be made out of wood (like a match stick) or glass (made from glass cutting scraps) or made of a hard rubber especially for this purpose. The blocks are placed between the edges of the pane and the neck of the glazing rabbet and held in place by the glazing point that also holds the pane. The panes have to be sized to allow enough space for the blocks. Blocks are placed no closer to the corners of the pane than one-fourth of the length of that edge of the pane. Usually two blocks at each edge are enough on panes up to 40".
A typical spacer block procedure for glazing vertically on a sash easel:
- Apply bedding putty in the glazing rabbet.
- Set the spacer blocks in place along the bottom glazing rabbet.
- Set the bottom edge of the pane on the spacer blocks.
- Ease the pane back into all of the bedding putty while holding the bottom edge in place on the blocks and seat the pane into its final position in the bedding putty.
- If needed, place blocks at the side edges and top edge of the pane. The blocks may need to be trimmed to fit the space between the edge of the glass and the neck of the glazing rabbet.
- Place a point at each glazing block to hold the block and pane in place. Place other points as needed.
- Continue with the front glazing as usual.

Fast-Track Glazing

Posted: Sat Nov 05, 2016 3:54 pm
by johnleeke
Consider this for "fast-track" glazing:
Consider using a water-based putty like AuquaGlaze, which can be ready for painting just a few of several hours after glazing.
Some putties, like Sarco Type M, are designed to skin over in less time that others, like Sarco MultiGlaze.
If using oil-based putty use whiting immediately after glazing to clean the glass. The particles of whiting bring oxygen to the surface of the putty, which speeds up oxidation and skinning of the putty. Dust whiting on the putty surface on day two and day three. Set up a box fan to blow warm air across the sashes 24/7. Air moving across the surface of the putty brings even more oxygen to the putty. Heat increases the chemical reaction of oxidation. Continue to use the fan between coats of primer and paint.
If you are uncertain about the outcome with new combinations of glazing methods and materials that you have not used before (and how they will react with primer and paint), I suggest doing a couple of test sashes well before the you have the main work scheduled, so if there is a problem you have time to correct it.
Keep in mind that forced drying of putty and paint materials can keep a fast-track project on schedule, but it can also effect the characteristics of the glazing that may limit its durability. The manufacturers assume "still air" drying and longer curing times when they formulate their products.
Be sure you are up to speed on the techniques to avoid wrinkled skin/paint due to shifting glass, which is likely on fast-track projects with inexperienced workers.
Glass may shift position after glazing, disturbing the putty before it has firmed up, resulting in wrinkles or tears in the painted surface of the putty. To prevent movement with smaller panes glaze vertically on a sash easel, with the sash in its final installed orientation, set the bottom edge of the pane directly on the neck of the bottom glazing rabbet when easing it into the bedding putty. After glazing Always keep the sash vertical in its final installed orientation during all handling and transport and installation. Larger panes may require spacer blocks:

Hand Brushing

Posted: Fri Aug 11, 2017 6:02 pm
by johnleeke
"Hand brushing" means applying all the primer and paint by hand, with a brush, without the use of rollers or sprayers.

I have some exterior wood field tests in place since the early '90s that demonstrate a performance difference between hand brushing and roller or spray application. Hand-brushing primer works the binder of the primer into the open cells at the wood surface resulting in a physical "keying" with the wood surface that results in longer lasting adhesion. Also, the hand brushing works the primer into any slightly open joints or weather checks that can be plentiful when maintaining older windows, helping to seal those slight gaps. With traditional oil-based top coats hand brushing tends to align the long stringy oil molecules parallel to each other, resulting in a more flexible longer lasting coating. My field tests were based on tests done at the Forest Products Laboratory by William Feist and others from the 1940s through the 1980s that demonstrated these same results.

Steve Jordan says, "You are absolutely right."

Re: Sash Glazing & Painting (with Video)

Posted: Fri Dec 22, 2017 8:55 pm
by johnleeke
The putty in which the glazier beds the glass is of four sorts:

--Soft putty which is composed of flour whiting and raw linseed oil
--hard putty composed of whiting and boiled linseed oil
--harder putty the same ingredients as the last with the addition of a small quantity of turpentine for more quickly drying it
--hardest putty composed of oil red or white lead and sand

The first of these putties is the most durable because it forms an oleaginous coat on the surface but it requires a long time for drying

The hard sorts are apt to crack if not soon well painted and the hardest of them renders it difficult to replace a pane when broken hence it is altogether unfit for hothouse and greenhouse work.

(source: An Encyclopædia of Architecture: Historical, Theoretical, and Practical, By Joseph Gwilt, 1847, page 587 )

Take the Time to Do It Right

Posted: Fri Jan 05, 2018 9:55 pm
by johnleeke
Many window specialists complain about how long it takes for putty to skin over. Why is that?

Because they are trying to emulate the corporate business model where "time is money," "faster is better," and "immediate gratification" of the consumer is a major marketing tactic. This sometimes results in conflict with the traditional methods and materials needed to produce effective results in this window work. A key component with many of these traditional methods and materials is the passage of time. Time for the putty to skin over, time for the paint to cure, time for your body to rest and recover from the intense work, time on a cold winter morning to enjoy the frost patterns on a pane of old wavy glass.

If you give time for the linseed oil in the putty and paint to dry slowly it will be more durable and give a longer service life.

I'm not talking here about working slow. You just arrange your work to allow for the "dry and cure" time needed without unduly inconveniencing your customer. For example, I've done housefuls of complete refurbishing without any boarding up. I do one room at a time usually 2 or 3 windows, fast neat and accurate just like you say: pull the sash, repair and prep the frames, install new custom sash that match the old (instead of boardup), then take the old sash to my shop for as long or short as needed for proper dry and cure times. In the mean time the customer has a normal room and usable windows. When the refurbished sash are ready they pop right in and the new fill-in sash are ready to go for the next room.

Sometimes the people I work for simply aren't interested in the longer service life the proper curing of traditional methods and materials can provide. Then the work can be done as zip zop fast as anything, use AquaGlaze and Snappy-Zippy Paint, who cares how long it will last, they are going to call me when they need maintenance anyway. I just advise them of the shorter maintenance cycle they will have. Funny thing is that most of the people I work for opt for a slightly higher price and somewhat longer project time to get that oh-so-good traditional durability.

Cut the paint line with a brush

Posted: Thu Feb 08, 2018 7:34 pm
by johnleeke
Cutting a straight line with a brush is essential to best practice in window work. It eliminates the entire step of scraping paint off glass, saving 5 to 10 minutes per sash. If you routinely face "stacks 'o sash", and do this work to earn money, how can you afford not to pick up on this basic window trade skill? I've taught ten year old boys and blue-haired grandmas how to cut to line on sash. You, too, can learn to cut the line.
Just practice on it for 10 minutes a day for 10 days straight. I guarantee your results will be improved. After using it on 20 sash complete your lines will be passable. Somewhere between 50 and 100 sash you will be a master of the Straight Line Cut.

Cracked Glass when pushing points

Posted: Mon Oct 29, 2018 3:52 pm
by johnleeke
To avoid cracking the glass when pushing points:

- Rock the putty knife and point from side to side, which eases the point into the wood.

- Use an angled putty knife so the force of driving the point is directly towards the wood and not angled down onto the glass as with a straight putty knife.

Lampson Bent Putty Knife
Supplier: Atlas Preservation, ... utty-knife

Posted: Tue Apr 02, 2019 8:32 pm
by johnleeke
How to keep window cleaners from damaging new putty.

With oil putties I always advise ABSOLUTELY NO window cleaning until one full year after glazing and painting to allow the putty and paint to fully cure and firm up. Then follow the step-by-step window cleaning method in the Window Preservation Standards book. This standard was written by Doug Johnson, a professional window cleaner and historic window specialist.
Here is the discussion that developed this standard over at the WPSC Fourm: ... f=27&t=267
You will note that the standard has a Quality of Results section with details on how to judge the quality including warnings on gouging fresh putty.

If you have an absolute requirement that cleaning must be done sooner that one year use a water-based acrylic glazing compound that firms up sooner, like Glaze-Ease 601 or Aqua-Glaze.

Also, always have the window cleaner clean just one or two windows first, then stop so the work can be inspected and approved before proceeding with the rest of the windows.

Keeping your hands clean

Posted: Wed Jul 03, 2019 6:25 pm
by johnleeke
Keeping your hands clean.

First, get less on your hands. Spread a rag out on your bench. Sprinkle a little whiting on it. Pat your hands on the whiting to coat your palms and fingers. Then pick up your wad of whiting and roll it in the whiting on the rag. Get the putty on the sash as quickly as possible, the more dillydallying the more putty sticks to your hands. Now less putty will get stuck to your hands.
Clean your hands frequently on a cotton rag during glazing, then again thoroughly when done. Wash your hands with detergent and hot water when done.