Sash Glazing & Painting (with Video)

Remove old panes & putty, cut & clean glass, putty & paint.
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Sash Glazing & Painting (with Video)

Postby johnleeke » Tue Sep 03, 2013 1:45 pm

(updates: 6/2020 note on not back bedding; 7/30/18 Clear Finish on Interior added lapping onto glass; [color=#FF0000]10/28/16 add Preventing Putty Wrinkles due to shifting panes; add details and procedure to Spacer Blocks[/color]; [color=#FF0000]8/2016 add to painting tools[/color]; 10/27/15 new section on skinning over; 6/12/14 link to glazing demo; 6/21/12 bedding details)

This method of glazing complies with the national Window Preservation Standards.

Basic overall procedure to refurbish windows:
(also see, Glazing & Painting in the book [url=][color=blue]Save America's Windows[/color][/url])

1. Remove sashes from frame, install temporary weather panel
2. Move sashes to onsite or remote workshop
3. Remove heavy paint buildup from frame and sill
4. Repair sills, paint sills and frames
5. De-glaze (remove glass) sashes, remove paint, cleanup
6. Mill out stock for replacement sash parts
7. Cut & fit stock for each sash repair
8. Repair wood of sashes
[size=150]9. Re-glaze and paint sashes[/size]
10. Move sashes back to site and distribute to window locations
11. Re-install sashes in frame and tune up for proper operation

Step 9. is detailed here:

[b]Sash Glazing and Painting Procedure[/b]

[i]"To glaze well, neatly and expeditiously, simple as the operation may appear, is an art not to be acquired in a day."[/i] --Daniel Cooper, master glazier, 1835

Video: Sash Glazing, Introduction, 10 min.

Video: Sash Glazing, Full Training Video, 36 min.

Video: Sash Painting, 9 min.

Glazing and painting a sash involves distinctly different materials:

Glass: brittle, stiff, easily broken by a sharp blow, readily cut to any size
Wood: stiff, strong, slightly flexible, swells a bit when wet, shrinks back when dry
Metal: tiny points to hold the glass in place
Putty: soft and pliable now, hardening to a resilient solid, ages to hard and eventually crumbles out
Paint: a sticky liquid now, drying into a flexible weather-resistant film

You weave these materials together creating a system that performs for decades to resist the weather, yet give you a view of the great outdoors and the universe beyond, and then fails in a graceful way, so the sash can be glazed and painted again.

The following procedure assumes the double-hung sash are new and un-primed bare wood, or have had all paint and putty removed down to bare wood, and that all woodwork repairs have been done.

Do not apply any treatments, primer or paint to the side edges of double hung sash. Leave the edges bare wood, which leaves a surface where the wood of the sash can dry out, preventing peeling paint and keeping the wood free of fungal decay.

9a. Pre-Treat.

A pre-treatment may not be necessary if all the wood is perfectly sound (as with all new wood) and a very effective primer is used, but I find I can lengthen the service life of the paint coatings on old wood with this "fine tuning" of the coating system. Scientific studies at the Forest Products Laboratory have clearly demonstrated that a paintable water repellent preservative effectively adds to the protection of the wood and dramatically limits fungal decay extending the window's life.

In many cases the exposed surfaces of the sash are weathered and need a pre-treatment, while the glazing rabbet is perfectly sound wood and needs no treatment because it has been protected from the weather by the putty and glass. In fact, a pre-treatment in the rabbet may prevent good adhesion of the putty because the oil of the putty cannot seep slightly into the surface of the rabbet. This must be balanced with the fact that too much oil can seep out of the putty, leaving the putty weak right along the surface of the rabbet, leading to putty adhesion failure. The proper balance is found in the worker who can judge the character of the wood and the putty to create a successful and long-lasting seal between the wood and the glass.

One of the traditional practices is to always pre-treat the glazing rabbet with linseed oil, or a linseed oil and turpentine mixture. This still works, but some scientific studies have demonstrated that linseed oil acts like food for the mold and bugs that damage paint and wood. A recent practice to avoid this is to use other materials to seal the glazing rabbet, such as alkyd-resin oils and primers, that are less like food to the mold and bugs.

If needed, apply a penetrating pre-treatment to the bare wood. Apply the pre-treatment to both faces of the sash, all muntin bars and muntins, possibly including the glazing rabbets. The bottom edge of the lower sashes' bottom rail may need treatment if it shows signs of deterioration caused by water; if the bottom edge is in good condition it should not be treated since it has done well for so many years without treatment. Do not apply pre-treatment to the side edges of the sashes, and the top edge of the upper sash.

There are two types pre-treatment, paintable water-repellent preservative and consolidating oil-resin.

Paintable water-repellent is suitable for sound wood surfaces. (if waxy paraffin type (Forest Products Lab's WRP Recipe, Thompson's WaterSeal, or similar) apply to all surfaces of the sash, if sticky oil or resin type do not apply to sash edges (the surfaces that run in the jamb's sash tracks) and face margins (the narrow strip where the face of the sash rubs on the parting bead or the stops)

Consolidating oil-resin treatment is suitable for gray weathered wood surfaces or surfaces that are somewhat "soft" or more porous than perfectly sound wood. The traditional recipe for this treatment is linseed oil and turpentine. I no longer use linseed oil because it is susceptible to mold and fungus attack. I now use a 1 part to 4 pats mix of turpentine and oil-based alkyd-resin varnish or a proprietary product, such as Flood's Penetrol, or similar.

When using an oil pre-treatment on the bare wood I try to do the next step (whether it is putty or primer), before the oil is completely cured and dry. This allows the oil in the putty or primer to "knit" together chemically with the oil that is in the wood providing better adhesion. If I wait until the oil treatment is completely dry the next putty or primer might not "knit" in and adhere quite as well. If I'm using a 50-50% mix of Penetrol and mineral spirits this might be in just 4 to 6 hours since Penetrol has a lot of driers in it. For a more traditional boiled linseed oil and turps mixture it might be 12 to 24 or more hours. The drying times might be different than this because it depends a lot on air temperature, air movement and humidity.

Just to confuse us all, there are some combination products that may be suitable. (California's Storm Stain Penetrating Wood Stabilizer, or similar) Water-based products of both types MAY be suitable, but all my experience and this recommendation is for oil-based products.

Penetrol is an oil-based product made of mineral spirits, linseed oil, alkyd resin and dryers that penetrates deeply into the wood surface. The mineral spirits evaporate leaving behind the oil and resin that cures and consolidates loose fibers at, and just beneath, the wood surface. Apply putty or paint primer when the pre-treatment is 80% cured. "80% cure" can be determined when the surface is still slightly tacky, and not yet "dry." The amount of cure time is dependent on weather or shop conditions. Penetrol is like a light varnish or like an alkyd-resin oil-based paint without the pigment.

Storm Stain is a waterborne product that contains zinc napthanate and a very tiny amount of resins. Zinc napthanate is a preservative that limits mold, mildew and fungus. The resins help hold the zinc napthanate in the wood, but there is not enough resin to consolidate loose fibers at the surface of the wood. Storm Stain does not penetrate as deeply as oil-based pre-treatments because it is waterborne. After 24-48 hours the water has evaporated, the wood surface is dry, slightly tacky to the touch and ready for paint primer.

9b. Prime. Do not prime the side edges of the sash that run in the tracks. Prime all surfaces of the entire sash with oil-based alkyd resin primer, except side edges and face margins. Prime the glazing rabbets if the pre-treatment was a water-repellent preservative. Do not prime the glazing rabbets if the pre-treatment was an oil-resin. This rule-of-thumb can be modified within following guidelines:

-- No priming or painting of the top edge of the upper sash because it usually doesn't need protection from moisture when the sash are single-hung or if double hung and the top sash is not operated
-- The top edge of the upper sash does need paint protection from the weather if it is a casement window
-- The bottom edge of the lower sash may need painting, especially if it had extensive deterioration due to moisture on the sill.

Allow primer to dry thoroughly.

9?. Clean glass, both sides, wet-wash method. Here is the complete method:

9c. Glaze.

Glazing Putty Types

Traditional Putty, Linseed Oil Type, knife grade, hardening (typically contains boiled or raw linseed oil, whiting)
specific products:
- Allback Linseed Oil Putty (can paint immediately with Allback paint)
- Crawford’s Natural Blend Painters Putty
- Old-Time (no longer available)

Glazing Compound, Modified Oil Type, semi-hardening (typically contains a mixture of oil types, linseed oil, soybean oil, mineral oil, plasticisers, drying agents, whiting, limestone, talc)
specific products:
- Sarco MultiGlaze Type M (skins over in a few or several days, for indoor use only, the good stuff)
- Sarco Dual Glaze (longer skin over, longer lasting in service, for outdoor use only, the good stuff)
- Glazol (can be good if you add a little boiled linseed oil)
- Perm-E-Lastic
- DAP 33 (for goodness sake, don't use this stuff)
- Perma-Glaze (no longer available)

Acrylic Elastomeric Type, flexible, gun grade (typically contains acrylic resin, water)
specific products:
- Glaze-Ease 601 (dries quickly for painting within 24 hours)

Acrylic Type, hardening
specific products
- Aqua-Glaze (dries quickly for painting within a few hours)
- Elmer’s Glaze-tuff

Ingredients in the various putty products: ... 1252#11252

Discussion on coloring putty: ... =6791#6791

Here's a formula from Justin Smith to calculate the amount of putty needed: ... rmula.html

For a brief explanation of the types of putty, and putty handling see this video replay of the live glazing demonstration: ... 30.86&fb=0

Setting the Pane
Apply glazing putty to glazing rabbets as bedding. Bedding seals the glass to the wood keeping water from interior condensation out of the wood. Sometimes the pane is not bedded in putty. Here is a comment on not bedding:

If working in a cold shop warm the putty slightly with a hot-air gun or infra-red lamp. Set the pane of glass in place and be sure the bottom edge of glass is actually resting on the neck of the lower glazing rabbet (for panes up to 18" wide). Jiggle the glass slightly so that it beds down into the putty, leaving about 1/16" of putty between the glass and the shoulder of the glazing rabbet, with some putty squeezing out all along the edges of the glass.

Preventing Putty and Paint Wrinkling after Glazing
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.

[color=#FF0000]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.[/color]

Install glazing points.
See the Glazing Points discussion here:
Swedish glazing pin-rods and triangular glazing hammer discussion: ... =4173#4173

Apply and tool glazing putty in the form of a bevel to make water-tight seal between the glass and the wood using the 3-step method: Place, Pack & Tool. Immediately "polish" outside of glass with whiting in a dry soft paint brush to clean oil from the putty off of glass and to "dust up" the surface of the putty. Flip the sash over and remove excess putty from interior joints and tool down to form water-tight seal at joint between the glass and the wood. "Polish" inside of glass with whiting. Set sash aside in correct vertical position to avoid settling of glass and distortion of beveled putty. Allow putty to cure and skin over for several days or a few weeks if possible.

Place, Pack & Tool. To get the line of putty to stick to the wood and glass use the 3-step method: Place, Pack & Tool. Place and pack each line of putty around the entire sash, it does not have to look good. To place the putty you can make little snakes if it is fun, but this wastes time; simply use your putty knife to quickly distribute the putty. Pack the putty into place by putting the end of the putty knife on the glass and wiggling the knife slightly as you force the putty in. Do this along all the lines of putty all around the sash. This gives the putty 5 or 10 minutes to 'marry' the glass before you start tooling. A little oil seeps out from between the particles of whiting and 'attaches' to the glass. This is actually a form of weak adhesion and it takes several minutes to happen. Then starting at the same corner of the sash, do your final tooling of the lines of putty.

Putty Knife. A 1 1/2" wide putty knife is good for most ordinary glazing. A slightly flexible knife can help the beginner keep from breaking glass or mashing over the arris of wood at the top of the glazing rabbet. A stiff putty knife is usually preferred by the professional because every time the knife flexes it is wasted effort and time. If you have a lot of sash to glaze or intend to be a professional start out with a stiff putty knife. Your putty knife needs to be clean and very smooth. The flat surfaces near the end of the blade should be so shiny you can see the reflection of a face well enough to recognize who it is. Clean and polish the surfaces with a rag after every use, stroking in the same direction that the putty flows when tooling. If your putty knife is not reflective you can polish it or buy a new one that is. Clean off and polish the surfaces with very fine steel wool, stroking in the same direction that the putty flows when tooling. To get reflective surface on an old knife we polish it on a hard cotton buffing wheel mounted on an electric motor arbor, with grey steel-polishing compound. Some new putty knifes have a clear coating to prevent rust, which must be removed or it will drag up the putty during tooling. Try a chemical paint remover. Do not simply scrape it off, you will scratch the metal and every one of those scratches tends to drag out the putty.

Polish the Glass.

Video: Polishing the glass is at minute 7:54.

Safety: Wear a respirator while polishing with whiting to keep the fine dust out of your nose, mouth and lungs.

"Polishing" the glass and dusting the putty with whiting in a dry brush right after glazing is a far more effective way to clean the glass, helps the putty to begin skinning over, and takes much less time than "wet washing" the sash after the paint has dried.

Get some whiting and take a few minutes to learn this simple method, you will be saving time immediately. Dip a dry brush in the dry whiting powder, then gently whisk the surface of the glass with the ends of the bristles. The whiting will stick to the surface of the glass where there is oil, showing where more whisking is needed. The surface of the putty will not be significantly disturbed if the brush has soft flexible bristles and the polishing is done with care. When the glass is clean, use the same brush to whisk away whiting that has built up in the corners of the putty.

Since the whiting-oil residue contains linseed oil, spontaneous combustion is a fire risk. Be sure to clean up thin dustings and little piles of the residue from around the glazing station immediately. Put the residue in a metal can filled with water. Do not use a vacuum cleaner for the clean up, since an accumulation of the residue might spontaneous combustion inside the vacuum cleaner and fire may spread outside the vacuum.

Types of Whiting
The natural product is ground chalk (calcium carbonate), which can have a range of particle sizes with some courser bits (not usually a problem with ordinary window work). The chemically formed product is precipitated calcium carbonate. The precipitated is a finer and more consistent material. Use only whiting made of calcium carbonate. DO NOT use other materials like pumice, diatomaceous earth, chalk line chalk made in China which may contain silica, plaster of Paris, baby powder, Durabond, etc., which may have significant health risks and are not proven by the traditional trades practice of using whiting.

Whiting Promotes Skin Over
The slight amount of whiting left on the surface of the putty is absorbed by oil from the putty. The whiting on the surface of the putty "kicks off" the skinning of the putty because it brings a small amount of air and oxygen into the outer layer of the putty. If you want a little faster skin over, come back with another dusting of whiting in 12 or 24 hours. But don't push fast drying too much--the faster the drying of the linseed oil, the shorter the service life of the glazing.

Whiting Suppliers:

Local paint dealers used to carry whiting, but few do today. Stained Glass shops use whiting and are often willing to sell out of their supply.

Whittemore-Durgin Glass Co. (stained glass supplier)

Talas Chemical Co., for the chemically precipitated type ... ctID=23686

Kelp4less at eBay, for the ground limestone type ... 519837a30d

Backing the glass.
Turn the sash over to see the bedding putty that has squeezed out. With the putty knife, slice out this extra putty, while tooling and packing it down into the joint between the wood and the glass. Remove all the extra putty from the wood and make sure that any gaps are filled with putty. Polish off the the glass with whiting.

9d. Wait for Putty to Skin Over

After glazing wait until the putty has "skinned over" before painting. The surface of the putty will dry and firm up into a "leathery" skin, while the rest of the putty beneath the skin will remain soft. Different putties and different environments will have different skin over times, which can range from a few days to several weeks.

Use your Judgement
Gently stroke the putty surface with a clean finger, if it feels oily it needs more time. If it feels dry it's ready to paint. If you are unsure it has skinned over enough, wait that much longer again.

Do a Skin Over Test
Also, when you are glazing, you can do a simple test: apply a few square inches of putty to a board, make it about as thick as your lines of glazing, maybe an inch wide and six inches long. Leave the test board next to your sashes as you wait for them to skin over. Then you can touch and poke at this test patch every few days to determine if the putty has skinned over. You can even make two or three test patches. Use one for touching and poking. When you think they have skinned over, you can try painting one patch to see what happens. If the skin of the putty wrinkles up, or something else goes wrong, wait for more skin over time, then try painting on the third patch. When everything goes well on the test patches, you know it's OK to paint the putty on your sashes.

Speed Up Skin Over
Keep the sash in a room with warm, dry air. Set up a fan to blow a gentle stream of air over the surfaces of putty. This brings more oxygen to the oil in the putty, helping it to skin over quicker. The day after glazing, give the putty another dusting of whiting. Each particle of whiting is coated with air, which contains oxygen. As the oil seeps out of the putty to surround the whiting particles, the oxygen helps the oil dry and the putty skin over sooner. You can even come back the third day for another dusting of whiting.
While there seems to be a big push to do everything faster, Faster, FASTER; keep in mind that the slower the putty skins over, the more durable your glazing will be. For longest service life, let your putty skin over slowly.

9e. Paint.

[color=#FF0000]Add to the painting tools listed in the book:
- Dusting brush, a big house painting brush or foxtail brush, to dusting off sash just before painting
- 6" drywall taping knife and razor blade, for trimming minor "over painting" on glass[/color]

Apply primer to putty bevels and interior seals, if needed and allowed by the putty manufacturer. Lap primer 1/16" onto the glass, painting "to the line," allow to dry. Apply two top coats of paint to entire sash except side edges and face margins and top and bottom edges if they are not being painted. (Use best quality exterior house paint. Waterborne 100% acrylic paint is good, as is oil-based alkyd resin paint.) Lap paint 1/8" onto to glass. If you can (with practice) lap the paint onto the glass just a bare 1/32" to 1/16", so much the better. Allow paint to dry and cure thoroughly. [color=#FF0000]Sand lightly with 220 grit sandpaper after the first topcoat if necessary to create a smooth paint surface without nibs or whiskers.[/color]
The over-paint-and-scrape-back method is problematic. Slopping paint onto a wide margin of the glass and then coming back to scrape it off takes more time than painting to a line. Slow down and learn to paint to a line, you will be saving time after three to five sashes. (Yes, you can learn to do it, I have taught 13 year old kids, and 72 year old grandmothers to do it, by showing them just once.)

Wet washing right after glazing and painting with solutions containing detergents or vinegar can cause paint failure along the edge of the glass within a year and may shorten the life of the paint and putty. Wait at least a full year for paint and putty to cure completely before washing glass.

[b]Clear finish on interior, paint on exterior of sash:[/b]

Here's my procedure for clear finish on interior, paint on exterior of sash:

Finish and Putty Schedule, step-by-step:

strip to bare wood
woodwork repairs if needed
prepare surface of wood (cleaning, sanding, etc.)
stain interior if needed
prime interior with thinned down varnish
coat interior with full coat varnish
pre-treat or oil exterior if needed (including glazing dados)
prime exterior with paint primer
set and glaze glass
coat interior with one or two coats of varnish that lap onto the glass
prime putty if needed
paint exterior with two coats that lap onto the glass

Sometimes the putty needs to be colored so it does not show white from the interior view, here are two discussions on this:

Historically, some sash were faux painted with glazes and graining to match varnished interior woodwork to get the better durability. On the exterior side of sash pigmented paint is usual because it provides better durability than clear finishes. If clear finishes must be used on the exterior of sash or the exterior window parts plan on more frequent routine finish and putty maintenance, perhaps at least every other year.

Oil-based spar varnish (long-oil type, made for the marine trade, with UV inhibitors, such as Man-O-War Spar Varnish) will be as good as any clear finish on the interior. Over all expect 5 to 8 year life, the top edges of the meeting rails and top of the lower rail may need spot maintenance every 2 to 4 years. The ultra-violet (UV) rays of the sun break down the UV inhibitors in the film of varnish after a few years and then breakdown the surface of the wood under the film causing peeling.

The old timers had this one figured out: paint holds up longer than any varnish. I see many old sash that were faux-grained on the interior to match the clear varnish or shellac finish of the interior woodwork. Often it's primer, one full coat of a solid color, one or two coats to get the faux-graining then a coat of translucent glaze that might be grained.

I use oil-based alkyd-resin varnish or oil-base long-oil "spar varnish" for sash interiors. I would not use poly-urethane because it does not take spot maintenance well. I have not worked with the acrylic water-based varnishes, but I suspect they would not last as long as oil-based varnishes. I have been testing shellac, which seems to require renewal every 2 to 4 years where direct sunlight hits it.

For clear finishes on the interior face of sash prep the surface by stripping and cleaning down to bare wood. Apply penetrating pigmented stains if needed to get the color required. Apply a thinned down coat of varnish to act as a penetrating "primer," apply one or two topcoats lapping down into the glazing dado. Color the putty with dry pigments to match the interior color of the stain. Bed the glass in colored putty. Apply colored putty in the usual way and tool to finish. Add one more top coat of finish on the interior face of the sash, lapping across the narrow line of bedding putty and onto the glass slightly.

Painting soft putty:
Use a medium-soft or soft brush and a light touch. It is possible to paint freshly applied putty, such and Allback's, and paint right away without damaging the flat surface of the putty. Some American paints do not flow out of the brush easily, which can cause problems with soft putty. If you are using Allback paint it is thin enough to flow out of the brush easily. American paints often require a "flow" additive, such as Flood's Penetrol for oil-base paints or FlowTrol for water-base paints. Just start doing it and adapt your materials and technique to give the result you want.

Brushes for Sash Painting:
My standard most-used brush is a "Purdy"-brand sash brush that is 3" wide and 5/8" thick on smaller lights. I use a 4" or even 5" house painting brush that is 3/4" or 1" thick for single-light sash with long lines of putty. The bigger brushes hold more paint so less time is spent dipping. The "sash brush" (about 1 1/2" x 3/4") provided in the Allback line is too stiff for me. Some sash painters use a 1" round brush with a conical shape at the bristle end for sash work, rotating the brush during the stroke, but this method takes too long for me because the brush does not hold enough paint, and the extra dipping slows down the work. I did use it once for tiny 3" x 3" lights and it worked well.

Have a variety of small to medium size brushes on hand, try out two or three and use the one that gives best results.

[b]Best Advice from the Pros:[/b]

Long Life. "The length of service life is controlled more by the methods and techniques used than by the products used. My own current shop standard practice is allow oil-based paints and putty a longer time to dry and cure. I use Sarco Type M for glazing in the shop, and Sarco Dual Glaze for glazing sash in place. About a third of the time I use other methods and materials for their special characteristics to serve the needs of special conditions for specific windows and projects. I have Allback paint and putty in 6 years of field testing and it seems good, but I'm not using it on whole projects yet. DAP 33 should only be used if you can't get anything else. If you are using DAP 33 you should be looking for something else." --John Leeke, Portland, Maine

Speed. "When training someone new to this, I emphasize that speed will come with experience. Technique is learned by doing. Start by concentrating on getting a good look. The technique, and the speed, will come naturally." --Steve Schoberg, window specialist, Plymouth, Indiana

The paint/glazing schedule above seems to work well for many people in many locations around the country. There are others that work as well or better.

Which paint/glazing schedule is better than another? This mostly depends on the methods you use, the micro-climate at the window and the general climate in your area. The only way for you to know for sure is to do a side-by-side field comparison. Do the left side of a lower sash one way and the right side another way. Keep good written notes on your methods and materials. In a few months or a few years you will know for sure which is better, for you, for the type of windows you work on, for the materials you can get.

Many window specialists have built "warming cabinets" or "drying rooms" to control the drying of their paints and putties during cold winter months and humid summer weather. They create a micro-environment with heaters, dehumidifiers and fans in order to speed up the work. However, speeding up the drying and curing rate of traditional materials like the drying oils too much will often give a shorter service life. Slower drying and curing rates extend the service life.

[b]Information Resources:[/b]

U.S. Army Construction Manual, Glass: ... ?iNum=1104

Paint testing manual: physical and chemical examination of paints, varnishes ..., by Sward, chapter 8.5 Putty, Glazing Compounds, Caulking Compounds, and Sealants.

Let us know the methods and materials you use for painting and glazing sash. Click on "Post Reply" above or below to ask questions or leave comments.

Copyright 2007-2012 John C Leeke

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Location: Portland, Maine, USA

Priming & Painting, detailed procedures

Postby johnleeke » Sun Nov 17, 2013 7:51 pm

Here is the detailed procedure I use to prime and top coat both sides of sashes at the easel. A curved painting rail is screwed to the easel posts so the sash leans on the rail, just the arrises of the upper stiles touch the painting rail so the rail does not disturb the wet paint.
(update: 8/2016 major corrections)

Lower Sash
. Start with lower sash exterior face bottom rail up
. Paint exterior "on the "Ls"
. Rotate sash 180 degrees
. Paint exterior "on the "Ls"
. Flip sash by pulling bottom rail out and up, set meeting rail down on easel
. Paint interior "on the "Ls"
. Rotate sash 180 degrees
. Paint interior "on the "Ls"
. Take sash off easel, holding by the edges with fingers in the ploughs and knot holes, then set down on cart with meeting rail up & paint top of meeting rail

Upper Sash
. Start with upper sash exterior face top rail up
. Paint exterior "on the "Ls"
. Rotate sash 180 degrees
. Paint exterior "on the "Ls"
. Flip sash by pulling top rail out and up, set meeting rail on easel
. Paint interior "on the "Ls"
. Rotate sash 180 degrees
. Paint interior "on the "Ls"
. Take sash off easel, holding by the edges with fingers in the ploughs and knot holes, then set down on cart with meeting rail up & paint top of meeting rail

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Posts: 173
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Location: Portland, Maine, USA

Re: Sash Glazing & Painting (with Video)

Postby johnleeke » Tue Aug 05, 2014 2:11 pm

For easiest compatibility when coloring oil-based putty use "earth colors," which are ground up stone and are very chemically stable and non-reactive. Grout usually has a lot of very chemically active binders in it--who knows how it will react with your putty. Usually dry powdered concrete colorants are earth colors and suitable for coloring putty and glazing compounds. If you need colors not available at the masonry suppliers go to the arts & crafts suppliers for earth color dry pigments. You might get a tan by mixing a little raw sienna with a little burnt sienna and just a hint of bone black. You could also use artist's oil paints with these colors.

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Re: Sash Glazing & Painting (with Video)

Postby golazo » Fri Aug 15, 2014 6:25 pm

"Penetrol is an oil-based product made of mineral spirits, linseed oil, alkyd resin and dryers that penetrates deeply into the wood surface."

Are we not trying to avoid linseed oil altogether based on your citing of research that linseed may harbor fungus? I've recently seen on a video by Baroque Painting on youtube a reference to a product from XIM which I assume is this product though, in the video only a reference to XIM is used without referencing which XIM product it is, they have four or five that could fit the bill of clear, penetrating type wood pretreatment.

The video using XIM is here:

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Re: Sash Glazing & Painting (with Video)

Postby johnleeke » Mon Aug 25, 2014 10:09 pm

That's right, so you would not want to use Penetrol where moisture is expected to be high and susceptible mildew and fungus.

All of this work is a balancing act, you have to balance the needs of the work with the materials available and methods that can be implemented--there is no absolute right or wrong way.

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Re: Sash Glazing & Painting (with Video)

Postby golazo » Tue Aug 26, 2014 10:48 am

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Re: Sash Glazing & Painting (with Video)

Postby johnleeke » Fri Oct 17, 2014 7:39 pm

If the wood surfaces are sound then a paintable water-repellent pre-treatment is suitable.

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Postby johnleeke » Thu Nov 06, 2014 9:29 pm

When glazing and painting sash and I need a fast turn-a-round, I routinely use Sarco Type M, polish the glass with whiting, blow a fan on the sash for two days, the second day dust the putty with whiting again, the third day, prime with California's fast-dry oil-based primer, fourth day topcoat with California's 2010 acrylic paint in the morning, anther coat in the afternoon; fifth day ready for install. This requires careful handling because the paint and putty is still tender and may not result in the most durable work.

If careful handling is not available and/or best work for durability is required then I prime the sash before glazing with slow-dry oil-base primer, glaze with Sarco Dual Glaze or Glazol, polish with whiting, 10 to 20 days for skin-over with no fan, one day for priming the putty with fast-dry primer, then three days for each coat of oil-based topcoat glossy enamel.

Slow work is more durable than fast work. Some of the people I work for are willing to wait longer and pay more for the slow work that is more durable.

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Production Glazing (with Video)

Postby johnleeke » Fri Apr 24, 2015 9:01 pm

This glazier has a high production rate without being in a hurry.

Interesting "speed glazing" techniques:
==> glaze on an easel
==> pick up two sash at once from the cart
==> pick up enough putty for two or more sash
==> glaze on the easy-Ls, then rotate sash
==> place putty with heal of hand
==> putty really soft
==> end-edge tooling with putty knife leaves no putty on glass
==> uses his hands, arms, shoulders and back to move the putty, not his fingers
==> concentrating on his work with no distracting radio blasting away

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Glazing Rabbet Prep (with Video)

Postby johnleeke » Sat Apr 25, 2015 7:07 pm

Use a "wet method" lead-safe technique to control the lead-health risk when preparing the glazing rabbet onsite. After deglazing, for final surface prep, apply linseed oil and turpentine with a narrow-spout bottle, then do the final scraping of the rabbet. The wet oil captures and holds the fine dust, making effective cleanup easier. Demonstrated by Chris Gustafson (Wood Window Restoration, Albany, Oregon):

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