Painting indoor side of metal windows (lots of them)

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I am undertaking to repaint the interior side of metal casement windows made in the 1930’s by a company called Crittal. The frame is about an inch wide and quarter inch thick. The windows run floor to ceiling and have six panes. I have about 10 windows to do. Each contains four sections so that works out to 240 panes worth of window! I’ve started on two windows and have spent far too much time. I’m hoping others will be able to give me some time saving tips.

The interior paint varies from badly flaked and rusted to slightly pitted and blistered to fairly good but chipped here and there. There are maybe five layers of paint on the windows. The exterior of the entire building was recently repainted by contractors so further progression of rust from the outside in should be prevented.

On the really bad areas, I’ve scraped what I can and have removed the rest with chemical strippers, but it’s very laborious. Better areas I’ve wet sanded to expose rust under blisters, but the problem is that it is very hard to feather the chipped edges of the sound paint. I’ve discovered that if I prime with red oxide primer I can then apply a fine finish filler to fill all the imperfections over the primer (I’ve been using the Mangers product) and it seems to really adhere well. You don’t normally hear of interior fillers being used on metal but I’ve been impressed by the adhesion to the primer. For big areas that have rusted away, I’ve used a product called “Rust Cure” from Screwfix that really works. It reacts with the rust to produce a solid black mass. I’ve filled over these voids with car body filler.

Does anyone have a better way to do this?

The putty (on the inside side of the window) between the frame and glass is presenting a new problem. It varies in thickness from 1 to 4 mm, depending on whether the glass has been replaced since construction. In the course of removing the built up paint, the putty has flaked away in spots and I cannot get a good edge without repairing it. Because the inside of the windows is subject to condensation, I’ve been using the car body filler (which is waterproof) to refill or top up the space between the window and glass. The filler adheres well but it has to be applied in many small batcher because it hardens in 5-10 minutes. What else can I use? Could I just put a thin layer of linseed oil putty over the existing putty that remains? Would it adhere? How about that Mangers product? It’s much easier to work, but I doubt it will survive the condensation, even if painted (or will it?)

Lastly, the sight lines are ruined by the exterior putty which is not very even and has been built up too high (so that it’s visible over the frame of the window). Is it safe to somehow cut down the putty on the outside and reseal it with paint to the glass?

Thanks in advance for any advice.
 
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I don't believe I can help too much on advising you of easier ways to repaint the metal windows, but I think I can help in regards to the putty problem.

Window glazing putty was used as a sealant around windows before there were any modern caulks or sealants. In a nutshell, what I'm suggesting you consider is using a modern caulk INSTEAD of putty. Caulks will adhere well to a metal or wooden window lattice, they're waterproof, they're paintable and they'll generally last much longer than putty will.

Is there a reason why you want to use putty? Is there any reason why you wouldn't want to use a modern caulk instead of putty in this situation?

If you do choose to use putty, you can probably get better adhesion of the new putty to the old putty if you thin some boiled linseed oil with paint thinner (or turpentine) and paint that onto the old putty so it wicks in. Then, bond the new putty to the oily old putty within a day or two, or before that oil is dry.

Do you know that you can improve adhesion of putty to wood by first painting that wood with linseed oil? The chemical reaction by which both linseed oil based putty hardens and "oil based paints" dry is exactly the same, regardless of whether that paint is linseed oil based, or an alkyd paint or a polyurethane hardwood floor finish or a true varnish on a violin.
Post again if you want me to explain all this.
 
Phew dh what ajob you got specially this time of year with condensation. Think whatever you do the rust will come back whithin 18 months as the gaps in putty over the years usually lets condensation seep behind the glass and rust is embedded where you can't get to, this usually means the glass panes start to crack as the rust scale builds up. However, people want them doing soooo! I normally just scrape off the loose, touchprime with red oxide (1930's unlikely to be galvanised ) I use body filler for any face filling (you can ****** the hardning time by reducing hardner) wouldnt use powder/ water based fillers here. The putties, I just scrape out any loose and use decorators caulk to fill round, angle the cut the nozzle as tiny as poss keep the cut flat against the putty and gently squeese keeping the nozzle moving, leave a min or so then smooth over with wet spat, (or my finger :oops: ). where the outside paint is showing above putty line let your interior paint come up to it.

If you need to strip them (arrrgh) we used to get most off by chipping with an old (sharp) wood chisel & hammer, goggles. It comes of a bit quicker than chemical , though Some bits neeeded nitromorse.

Coo it's late. Hope you find somthin usefull above.

good luck .
 
Nestor and Confident, Excellent advice, both of you. Really appreciate it. I'm going to print it and save it. Couple of questions, though, on what you say...

Regarding caulk. I agree it's got to be better than putty. But I've had very poor results with the so called acrylic caulks or "decorator's" caulks. They shrink massively and leave an ugly depression over the gap. Silicone doesn't do this, of couse, but you cannot paint it. Is there a particular product that is paintable and doesn't shrink? If there is one, I'll run out and get it tomorrow!

Confident, you're not keen on my fine surface filler idea? Why not? It's going on a primed interior surface which will be sealed with oil based paint. The filler doesn't need to "know" that there's metal under that paint it's sticking to! Or do you think there's something more going on? Maybe the temperature changes in the metal? But the instructions say ok for exterior as long as sealed with paint. And it goes on and sands soooo nicely!

You mention condensation. Hmm, hadn't considered that. What's the risk and what precautions should I take?

Thanks again, guys.
 
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Nestor and Confident, Excellent advice, both of you. Really appreciate it. I'm going to print it and save it.

Im going to print it and publish it!...
 
DH05 said:
Regarding caulk. I agree it's got to be better than putty. But I've had very poor results with the so called acrylic caulks or "decorator's" caulks. They shrink massively and leave an ugly depression over the gap.

Confident, you're not keen on my fine surface filler idea? Why not? It's going on a primed interior surface which will be sealed with oil based paint. The filler doesn't need to "know" that there's metal under that paint it's sticking to! Or do you think there's something more going on? Maybe the temperature changes in the metal? But the instructions say ok for exterior as long as sealed with paint. And it goes on and sands soooo nicely!

You mention condensation. Hmm, hadn't considered that. What's the risk and what precautions should I take?

Thanks again, guys.

Hi DH, The condensation. Merely that its a nusiance this time of year especially on metal windows, a day like today (+4) they probably would not dry out unless they face south and you got a blow heater in room.
The caulking.Yes if you try to fill a hole or say a deep screw hole it will sink but another apllication will flush it off, most fillers require a second fiinish unless you overload and sand. Caulking really is for gaps along skirting/wall for instance. The small cracks on putties on interior crittal frames should easily fill in one go. I use geocell decorators caulk/ dow corning. from Brewers/ hurst etc. Dont use the shed stuff it's erm awfull. The other problem you may get with the caulking is back to condensation, caulk is acrylic so if you can't get caulk to dry before windows start condencing the caulk will not go off and will make a mess.
I know it's tempting to use that filler but the filler will move in different ways to the metal and over time this will minutely crack the paint allowing moisture in making the filler swell/ blow. Its really for plaster/wood. Unless it's new (I dont know efryfin :LOL: ). Though have to say years ago up top shift of multi storeys scraping cement off crittals was a bugger.
hope you can make some sence out of above good luck.
 
DHO5: You said:

"But I've had very poor results with the so called acrylic caulks or "decorator's" caulks. They shrink massively and leave an ugly depression over the gap."

That shrinkage occurs as the caulk dries. The same thing happens in emulsion paints, it's just that we don't notice it because the paint is relatively uniform in thickness, and so the shrinkage in the paint film as it dries is also uniform. Caulk varies in thickness, and so the shrinkage varies in proportion to the thickness as the caulk dries, resulting in the depression you noted in the dried caulk.

Open your yellow pages to "Caulking Equipment & Supplies". I expect the companies selling caulk to the caulking contractors in your area will have a well educated opinion on what caulk might be suitable in your application. I'd definitely ask them if they can get a synthetic rubber caulk called "Kop-R-Lastic". I use it on all my windows because when you want to remove it, it pulls off just like a rubber rope, and that makes maintaining the caulk on windows and doors a much easier job because very much less time is spent removing the old caulk. You can also get single component moisture cure polyurethane caulks that have excellent adhesion and certainly have the strength to hold the glass in place as securely as any putty would, but I'd be concerned that removing them would be a lot of work.

I think if you phoned your local caulk distributors, you could get more knowledgeable advice than I can offer, and it'll be about caulks that are readily available in your area.
 
Hi

3 years on and its my turn! Having lots of "fun" stripping the windows (inside and out) back to bare metal with nitromors and other chem strippers, heat gun and all to quickly blunt scrapers. No idea if there is an easier way but if anyone knows of one, your tips would be much appreciated!

Problems:
1. paint not sure which is the best paint - I've tried Hammerite primer and "direct to rust" both of which seems too "gloopy" and shiny and doesn't seem to stick easily or evenly - I was very careful to keep stirring them regularly. International matt black paint seems too dull. Does anyone have any good tips as to which paint works best (exterior and interior), and will not be too shiny or dull?

2. fillers - lots of holes in wooded frame - was proposing to use exterior wood filler - anything better to use please?

3. putty - difficult to remove - any tips how to remove quickly and what to use - caulk or putty?

Thanks for any tips fellow sufferers.
 

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