Hello everyone,
Is there a process, that eliminates, the growth of mold on the surface of Glazing Compound? I see an old window, with dark black mold on one leg of the glazing, why? A friend just had a large livingroom window, re-glazed, with Latex window glazing, it’s mostly turned black, why? On the job I’m about to work on, a reglazed window, the glazing painted with exterior acrylic latex, appears to be glossy and beautiful after several years. No mold, why? What did the previous craftsman do? I’ll appreciate your input and look forward to your responses. Thanks
Replies
I'm just guessing here....
When the glazing is applied, it should be allowed to skin over before painting. I understand this can take up to a few days if the weather is wrong. Perhaps painting it before it skins leaves it more likely to mold.
That seems less and less likely to me as I typed it out.
Was the recent glazing that is now black painted? Painting is necessary.
Does the window with the mold get much sun?? If the window is in heavy shade but not well sheltered from the rain it will stay wet a long time and then mold.
Rich Beckman
Another day, another tool.
Hi Rich,
Thanks for answering. The aluminum windows, are in mostly a shaded area and were not painted. The wooden windows I've observed, are also in a shaded area and also, were not painted.
I guess, if I break this down, from the finish backwards, what I'm really asking is will mold and mildew grow on the finished surface and if so is it more likely to grow on an latex or an oil based surface?
Will it grow directly on the glazing compound? the answers is yes.
Will it grow on the window sash, the mullion or muntin and proceed through to the surface? In other words can it be smothered by the layer of paint?
Also, is a primer such as KILZ, a way to stop the mildew from the lower layers?
One last question, have you heard of "Zingers"primer? Thanks for your time, Will
"In other words can it be smothered by the layer of paint?"
No. If mildew is painted over, no matter what the paint, the mildew will come through.
The mildew needs to be cleaned and the surfaced disinfected with bleach (see Goldhiller's post).
Kilz, Zinser, Bulleye are all made by the same company. I don't remember which primer would best fit your needs. Perhaps call the company, I'm sure they would be helpful.
When glazing a wood window, after removal of old paint and glazing, I prime the wood, let it dry, apply the glazing, let it skin, and then paint. I don't prime the glazing. Maybe I'm doing it wrong.
I've never done an aluminum window and I'm not sure if it should be primed or not before glazing.
As Goldhiller mentions, you can get a fungicide additive for the paint (some paint comes with the fungicide already in).
I would think that it's possible, especially in a shaded area, that mildew is inevitable and periodic washing/disinfectent is necessary. Wouldn't be much of a job if done often enough (2x year?).
As to whether oil or latex is more prone to mildew, I don't know.
Rich Beckman
Another day, another tool.
Rich,
I do things just a bit differently, I guess.
Just for clairification and not because you stated otherwise.......when placing new glazing on a new window, the wood is always pre-primed with oil primer.
When placing new glazing, either new or replacement, I apply a light coat of boiled linseed oil with a small brush immediately prior to laying the glazing, on both the wood and the glass. On old wood, this prevents the wood from sucking the new glazing dry..... and in both cases, it quite literally glues the glazing in place when that linseed oil finally dries under there.
I always prime my glazing after several days of dry time with an oil-based primer prior to painting with any paint. Having foregone that step a couple of times over the years on a couple of windows, I've seen the premature failure by comparison. I don't skip that primer anymore ever. Of course, this adds a day or two of primer dry time before the topcoat should be applied, but I've discovered it's well worth the effort and the wait.
Anyway, these are the procedures I use with Dap 33 and it works for me. The windows on this house here are still bearing the same glazing I applied to them in the fall of '87 and it's still in great condition.
If storm windows are allowed to suffer on the inside from winter condensation, the wood under the glazing can get damp from underneath even if the glass is bedded as it should be, and this can lead to premature failure also. The bedding helps a whole bunch though in forestalling that occurance under those circumstances.
Knowledge is power, but only if applied in a timely fashion.
You have decribed the proper method for window glazing as best I can remember. Your boiled linseed oil use is excellent. Boiled linseed oil is a medium length drying oil. It does not gennerally support the growth of mold or mildew unless it has been contaminated and stored in a wet/damp location for an extended period of time. You do not use the more convenient latex glazing material, but stay with the tried and proven Dap 33, which, by the way, also contains boiled linseed oil. Metal sash windows should not be glazed with Dap 33 or latex glazing compounds. Dap makes a gray colored (can't remember the number) glazing putty specifically for metal sash windows. When using either type of glazing putty you are also correct in that they must dry for several days b/f painting. Painting to soon will prevent the drying oil in the glazing putty from curring completely, and the paint will mud crack or peel off the uncurred putty. Water gets in the glazing and the failures start.
Good advice from both you and Rich
Dave
Dave,
For metal windows, I use a gray glazing compound that I usually get from the glass shop in town here called SarcoSeal which is formulated for use with either wood or metal. I've used it many times for wooden window sash and it's just as good there. Excellent product that I'll gladly recommend provided it's installed, primed and painted properly.
Knowledge is power, but only if applied in a timely fashion.
To further clarify, please.....
You make sure the wood has primer on it, and after the primer is dry you apply the boiled linseed oil and immediately apply the glazing.
Is that correct?
I've never used the linseed oil, but I haven't done that much of it (but maybe a few panes in the not too distant future).
Thanks,
Rich Beckman
Another day, another tool.
Rich,
You got it right.
And I recommend getting the linseed oil on the glass, too.
All the smears from the glazing compound and the boiled linseed clean off easily with some glass cleaner, paper towels and a razor knife or similar once everything has dried. I wait until I'm all done priming and painting and the paint has dried for at least a couple of days. Then do the cleanup.
Be careful that you don't allow your knife/razor blade to penetrate under the glazing during cleanup or you've just broken the seal you need to maintain for an effective and longlasting job. if it does, carefully push it backdown into contact with your finger. If water gets under there and freezes, it can pop the glazing in the first winter.
Also watch what you do with your fingers as you handle and mount any storms as that glazing compound will be nice and soft at this point.....just the way you want it to be.
Knowledge is power, but only if applied in a timely fashion.
Goldhiller,
Thanks! Next time around (whenever that is) I'll try it that way.
Rich Beckman
Another day, another tool.
"I see an old window, with dark black mold on one leg of the glazing, why? A friend just had a large living room window,
re-glazed, with Latex window glazing, it's mostly turned black, why?"
Were both of the above unpainted glazing? Just applied and not painted?
If so, there's food/nutrition in window glazing for the mildew. Older/conventional glazings frequently contained boiled linseed oil, for example, or boiled linseed may have been added or used as a sealer underneath. I do this when I glaze. Left unpainted, the glazing would be an open buffet for mildew. Today's latex glazing may also contain a viable food source.
Or it is possible for mildew to get a start on the bare substance and then come thru the later applied paint if that mildew was not exterminated first with bleach.
Those are my best guesses as to the cause of what you saw.
Thank you for taking the time to answer my questions, regarding glazing compound. To answer yours, the aluminum window, with the newly applied Latex Window Glazing, was not painted. The double hung wooden window, with the divided light wasn't painted either.
If I am to understand what you're saying, the mildew, doesn't grow in the latex paint, applied to the surface, but rather in the galzing compound itself. Or on the subsurface, such as the wooden frame/mullions, muntins & sash, of the window.
The skin created by the curing of the glazing compound, protects it, followed by the coating. Would you recommend, wiping the skin with bleach or alcohol, before painting?
Does this mean then, that the use of oil based paint, can cause growth on the surface, even after the glazing compound has skinned over?
Thank you again for your time, Will
Mildew will grow on virtually anything, but if provided with an extra handy and nutritious food source, that's where it will set up housekeeping first and thrive to the Nth degree.
I don't think the skin on the glazing compound provides any real discouragement to mildew growth, but a layer of paint (oil or Latex) does although it only deters it. If damp conditions are provided, it will grow on most anything. Some surfaces are just more hospitable. It seems the glossier the surface, the less hospitable...in general.
Applying some diluted bleach to infected or suspect surfaces and then rinsing well after 5 minutes or so is a good pracice. Otherwise infected areas will still be harboring the spores underneath. Allow any treated areeas to dry well beofre painting, fo course. A fungicide additive in your exterior paint is always a good idea too.
Knowledge is power, but only if applied in a timely fashion.
Hello Rich ,
This is so very cool, to have you guys, as a resource. I want to return the favor of passing on valuable and accurate information. You'll probably be disappointed to find out that I'm a local singer songer writer and play gigs here in Houston as well as give guitar lessons. I've done this actively for 30 years. I am interested in anything that has to do with houses, since my late stepfather was a master carpenter and he left us, before I could learn what he knew. So, here's what I've assimilated so far;
Mold & mildew, mold in particular, have been around for billions of years. In a way it's not my mission to destroy them, just keep them off the paint. Since, mold is part of the Fungi family, it is a single cell organism, that has a creative genetic code. It's job is to survive. If oil based paint or latex paint is applied to a plywood (soffit) substrate, without a competent primer, our little guys will show up, dig in and go to work, as soon as the plywood begins to knuckle under. Since, mold lives on decaying material, it will be very happy if it's flight plan lands it on a badly prepared surface.
There doesn't seem to make much difference, between the oil based finish coat and the latex. As long as it's inorganic, mold spore has the inherent patience, built into it's genetic code to lie in wait, indefinitely. What does make a difference, is the sheen. A high gloss finish, washes away the little spores, so they never have a chance to attach themselves. As far as science is concerned, at least at Rice University, they can and will land on the unfinished skin of the glazing compound, but after the skin dries, which can be accelerated, with the gentle and careful use of a heat gun, the spores that did make it, and rest assured, they will be there, can be covered, like a coffin, with, KILZ primer, and a coat of gloss or high gloss oil or latex, to lay dormant, until the sun's radiation opens the surface, or until the next coat is added.
It's debatable whether the linseed oil is better as a primer, against the raw wood, or the KILZ, or some other primer. What is certain, is the bond between the linseed oil in the DAP33 and the linseed oil on the freshly stripped and cleaned surface of the old wood. The use of the Latex window glazing seems to change the layering and call for priming with KILZ, or in my neighborhood, the Murphy Bros. recommend, their version, by Pratt & Lambert. Either way, mold spore has shown it's resilience to earths constant life and death cycle and will be there to deal with. According to the science lab at Rice, the linseed oil is a much better feeding ground for the mold than the latex paint. So, a primer on the surface followed by a high gloss exterior coating and annual washing with bleach are recommended.
I've found one window, that survives, after four years, in our environment, and in the shade, with sprinklers adding moisture to the already high daily humidity. The Mullions are trimmed with DAP33, primed with KILZ, finished with two coats of high Gloss exterior Latex, with bleach rinses between applications.
How am I doing, so far? Will
Hello Goldhiller,
This is so very cool, to have you guys, as a resource. I want to return the favor of passing on valuable and accurate information. You'll probably be disappointed to find out that I'm a local singer songer writer and play gigs here in Houston as well as give guitar lessons. I've done this actively for 30 years. I am interested in anything that has to do with houses, since my late stepfather was a master carpenter and he left us, before I could learn what he knew. So, here's what I've assimilated so far;
Mold & mildew, mold in particular, have been around for billions of years. In a way it's not my mission to destroy them, just keep them off the paint. Since, mold is part of the Fungi family, it is a single cell organism, that has a creative genetic code. It's job is to survive. If oil based paint or latex paint is applied to a plywood (soffit) substrate, without a competent primer, our little guys will show up, dig in and go to work, as soon as the plywood begins to knuckle under. Since, mold lives on decaying material, it will be very happy if it's flight plan lands it on a badly prepared surface.
There doesn't seem to make much difference, between the oil based finish coat and the latex. As long as it's inorganic, mold spore has the inherent patience, built into it's genetic code to lie in wait, indefinitely. What does make a difference, is the sheen. A high gloss finish, washes away the little spores, so they never have a chance to attach themselves. As far as science is concerned, at least at Rice University, they can and will land on the unfinished skin of the glazing compound, but after the skin dries, which can be accelerated, with the gentle and careful use of a heat gun, the spores that did make it, and rest assured, they will be there, can be covered, like a coffin, with, KILZ primer, and a coat of gloss or high gloss oil or latex, to lay dormant, until the sun's radiation opens the surface, or until the next coat is added.
It's debatable whether the linseed oil is better as a primer, against the raw wood, or the KILZ, or some other primer. What is certain, is the bond between the linseed oil in the DAP33 and the linseed oil on the freshly stripped and cleand surface of the old wood. The use of the Latex window glazing seems to change the layering and call for priming with KILZ, or in my neighborhood, the Murphy Bros. recommend, their version, by Pratt & Lambert. Either way, mold spore has shown it's resilience to earths constant life and death cycle and will be there to deal with. According to the science lab at Rice, the linseed oil is a much better feeding ground for the mold than the latex paint. So, a primer on the surface followed by a high gloss exterior coating and annual washing with bleech are recommended.
I've found one window, that survives, after four years, in our environment, and in the shade, with sprinklers adding moisture to the already high daily humidity. The Mullions are trimmed with DAP33, primed with KILZ, finished with two coats of high Gloss exterior Latex, with bleach rinses between applications.
More to come. Will
p.s. I'm new here and would have sent this to both of you, but can't see how, yet.
Well, thank you for the more detailed info.
Although I've never spent any extended period in Houston, I have a friend who lived there for years and visited once. It was everything he described; like the most humid part of summer in NW Illinois...only worse.
I can definitely imagine what you're fighting with down there regarding mildew problems. You have my sympathies. <g>.
Knowledge is power, but only if applied in a timely fashion.