Painting sash window nightmare

[88v8]

Rotten situation to find oneself in.
32 windows... caramba. Is this Osborne?

Anyway, another vote for Bedec. I've tried linseed, and would use it for black on south facing, but otherwise the drying time kills it for me.

I don't use water base indoors, but outdoors it does seem to be better.

I've seen so-called professional painters wipe the rain off windows and then paint them... the job should only be done at the right time of year.

That failed paint needs burning off and start again.

Some of your pointing has holes in it.... another job....

Zinsser doesn't have much retail penetration, bit specialist, probably why it doesn't get mentioned. Some that they describe as 'breathable' is only marginally so.

 

[Stevers]

I haven't been on this forum for long and only viewed a couple of threads, but I haven't seen any recommendations for Zinsser Allcoat Exterior. I painted my c1910 sash windows using it in Sep 2020 and it's looking good. Seems to be liked by decorators too, any reason it's not getting mentioned here?

Is that the water or solvent based version? When we moved here in 1997 International Ranch Paint (IRP) was still available and I got great results with that, although my experience is that it needs very good preparation to get anything other than IRP to stick to it. IRP was self-priming and claimed to be microporous, that not after about the third or fourth coat if I remember correctly.

This is a really interesting and useful thread. My sash windows were painted with IRP in about 2000 and other than retouching some of the cills, bottom rails and putty beds these have lasted really well although none are true south facing - all mine being either south-east or north-west facing. Seeking an alternative to IRP I settled on Zinsser All Coat (solvent based). It's likely that I'll paint my windows this year using AllCoat [Ed] that I've tinted to a rich cream colour, although I'm open to better options. I'm planning to tackle any defects in the cills with epoxy hardeners and fillers, and to replace any failed putty beds with Timbaglaze polymer glazing sealant. It's too early to say whether Zinsser AllCoat is as long lasting as IRP, but I suspect not. All Coat and IRP are/were self-priming and much easier to use on a mix of bare wood and sound existing paint.

Single glazed sash windows are excellent dehumidifiers - trying to put a good spin on it! It's worth making sure that the inside bottom rails of all sashes are well painted as water ponds there. I stripped all of mine to bare wood and applied several coats of Owatrol until they would take no more. As satin oil paints are not self-priming I must have then used a 'universal' primer before the top coats. This was before I retired, and perhaps nine years ago, so they're lasting well. Owatrol is mainly sold as an additive to help paint flow, and while I'm not at all convinced by this use, it is an excellent rust proofer. There are dire warnings about discarded rags spontaneously combusting on the tin, and it crusts up and smells just like Linseed Oil, so it's very likely to be Linseed Oil with thinners and driers.

 

[marlonhambo]

Is that the water or solvent based version?

It is the water based version. I didn't actually know there was a solvent based as well. But anyway I don't like working with oil, I'm too messy

I've actually started using Zinsser Allcoat internally too. The Dulux quick dry I was using is horrible and I didn't want to buy another tin to finish the internal woodwork. 1 hour recoat is a bonus.

 

[a twig]

Zinsser doesn't have much retail penetration, bit specialist, probably why it doesn't get mentioned. Some that they describe as 'breathable' is only marginally so.

Definitely an approach with caution company - a very enthusiastic marketing dept with a hand waving approach to heritage and breathability - but there are some great products to be had from them in the right application.

 

[Toby Newell]

Hi, I’m new hear and just need your advice. I’ve just had all my Victorian villa sash window renovated sanded and now painted to a great expense in the Isle of Wight. In 4/5 months the paint has bubbled and cracked and not adhered to the wood. Mainly on the bottom of the sashes and the sills. For your information the painter did not strip the old paint off just sanded. I’ve had the painter back with his so called specialist friend and has told me the wood has no juice left in it and is dead. That’s why the paint he used (He says the best Weathershield 12 and 3 ) is not adhering to the wood. He also tells me that the old sashes at one point had been varnished so once again it makes painting old sashes hard because the varnish is in the grain. His out come would be to replace all the 32 windows. I was like that is not an option and need another opinion. That is why I’m turning to you guys for some well needed help. Is there a specialist product out there that I can use to paint the window with that will actually work on 100 year old windows. Just to also confirm that the Weathershield did work on the new replacement wood and sashes so I do see his point, but there must be a way to save my windows and paint the 100year old wood. Thank you in advance to professional advice.

View attachment 10593

View attachment 10594

View attachment 10595

View attachment 10596

"For your information the painter did not strip the old paint off just sanded"

This is incorrect, especially on older buildings, I almost never overcoat and if I am asked to do so, I explicitly caution the customer. There may be lack of adhesion and / or a chemical reaction.

"wood has no juice left in it and is dead" this is either what we call in the trade 'complete and utter bollocks' or it could display a lack of communication skills, what he might of meant was 'the timber looks old, perished and cracked' to which he should of informed you of the viable options, which would be:

1. Strip back via mechanical means / scraping, sanding.

2. Stabilise any weak or cracked wood with wood hardener.

3. Sand back wood hardener leaving only in interstices.

4. Fill with two part filler.

5. Prime and repaint with breathable paint.

OR.

6. Excise rotted sections and replace.

" it makes painting old sashes hard because the varnish is in the grain"

This is both true and also sounds like a bollocks excuse, what he should of added is 'it's a lot more work but we can remove the old varnish with a solvent stripper and wire brush' either he is not aware of how to do this or more likely doesn't fancy the effort.

Scanning another couple of posts, apologies for not reading the entire thread, but in general:

True, third party trades insurance does now normally exclude hot work and open flames, however, er, plumbers and gas engineers... so of course you can pay for a hot work ammendment, which all exterior painters should have.

Breathable paint. Ok, so linseed oil is a horrible product, but the paints are quite breathable, however.

As a finisher I have used £ tens of thousands of finishes and have studied finishes for over 30 years.

Linseed paint is good, if slow drying and it is traditional, but there may be better performing alternatives. It's like Roman concrete, it's very good, but you don't build a bridge out of it.

Look up Sikkens (owned by Akzo Nobel) they make excellent paints and stains, they spend (parent company) £ Billions in R&D to create breathable, durable and anti fouling paints etc. If you have a £100m project with a wood exterior of several thousand sqm, you don't use linseed oil, you use Sikkens...

A little trade info here, one of the main differentiators between DIY and professional products are the application characteristics. Despite possible similar final properties (appearance, durability etc) professional products are normally quicker to apply with quicker drying times due to time/cost relationship in industry. Professional products may actually be harder to apply but should be cheaper for a professional. So linseed oil paint may be a good option for a DIYer with a small area but it might be more cost effective on a large job for an expert to use a more highly engineered product. Similar result, less time.

Finally, a little science. ALL paints are somewhat breathable and NO paints are totally breathable, it's finding the right balance. There is obviously a lot of woo woo floating about as 99.99% of people's knowledge of physics, chemistry and coatings is, understandably, quite low.

And that normally goes for 99.99% of the people selling it too. Ask me how I know.

The basic rule is, there's no point putting a GoretexTM gaiter over a thigh high rubber welly... ie you need to strip any timber perfectly clean, to the grain before you apply any microporous (breathable) coating.

Otherwise the only thing breathing, is your welly.

 

[Toby Newell]

Ok I feel I’m getting somewhere. Just a couple more questions.

So from what your saying the key is that the painter hasn’t sanded/stripped down enough and left old paint on that doesn’t let the wood breath. Hence the water trying to escape when the new paint is on. So with this in mind, that’s why you say we need it to go to bare wood.

1- So my question is why do I have to use bedec/ specialist paints on old sash windows? Is the wood different? Is it because of the age of the wood and how they have been treated prior. Sorry for my ignorance I just need the whole story before I go back to this idiot.

2- They said they wanted scaffolding prior which was more secure for them to paint. . How high can a scaffolding tower go to feel comfortable and secure. My windows are on the second floor.

3- Painter told be they can’t burn off the paint useing a heat gun because his insurance won’t cover it in case he burns the house down. Is this true in 2023 ?

May I also add, I am very sorry to hear you have had issues, I see this often, it must be very upsetting.

Please see my main post but yes, for a large job scaffolding is a no brainer, you only have one life. I guess IOW might be slightly more windy than some parts of the UK. You can make scaffold towers more secure with lashings and bracing outriggers but they are still less safe and more restrictive. Working at height is both dangerous, tiring and a pain anything that makes it easier and safer is welcome. I have refused foremen who told me I have to run up a 5m ladder to work, you don't.

Safety at height is one of the few areas of Health and Safety legislation that hasnt gone mad, how high is a horse? Too high for Superman to cope with.

Apart from that everything else they told you was BS. Unfortunately they do not appear to be high quality individuals.

You can at least ask for a part refund of the defective areas then try and find someone decent to redo those.

 

[malcolm]

£5K scaffolding is unreasonable in my view for painting windows. You can get up to second story very safely with a modern scaffold tower. I've got the 9m version one of these: https://www.laddersandscaffoldtowers.co.uk/acatalog/Trade-Master-Professional-Scaffold-Towers.html which is still under 1.5K

Safety at height is really important. I'm forever having to do training courses to work up there and I hate heights. The first thing the training says is don't use a ladder. You do need good outriggers on a scaffold tower after you put the second level on otherwise it is very dangerous. Extend the outriggers when you put a third level on.

The trades might ask for the scaffold tower to be tied to the building. Stainless threaded eye bolts resin fixed into brickwork should work for that. You can unscrew them or break them off when the job is finished or leave them up for next time.

 

[Toby Newell]

£5K scaffolding is unreasonable in my view for painting windows. You can get up to second story very safely with a modern scaffold tower. I've got the 9m version one of these: https://www.laddersandscaffoldtowers.co.uk/acatalog/Trade-Master-Professional-Scaffold-Towers.html which is still under 1.5K

Safety at height is really important. I'm forever having to do training courses to work up there and I hate heights. The first thing the training says is don't use a ladder. You do need good outriggers on a scaffold tower after you put the second level on otherwise it is very dangerous. Extend the outriggers when you put a third level on.

The trades might ask for the scaffold tower to be tied to the building. Stainless threaded eye bolts resin fixed into brickwork should work for that. You can unscrew them or break them off when the job is finished or leave them up for next time.

I never use towers, a freind of mine has two large towers, scaffold is much easier to work off of, it really depends on the layout, sometimes it's no sweat but often it's a palava to move them and sometimes places are only reachable via scaffold.

No idea on costs but bear in mind small island mentality, I know it's not as bad as the channel islands but I would wager some things being more expensive as they have to be shipped from the mainland, near as it is, also, less competition.

But seeing as these painters appear to like wearing big hats and eating baked beans, they probably overcharged.

 

[Stevers]

This could be controversial.

If the sash windows are wide enough for a human bottom, they can be painted sitting on the cill, body out with legs inside. That's how I do my second floor windows. Granted anyone that sees it freaks out (a bonus), but as someone not keen on ladders at that sort of height, it doesn't feel overly precarious. Perhaps someone could hold onto legs, or something heavy could be found that legs could be hooked round, at least to start with. I have painted first floor windows that way in preference to working off a ladder as I find it more comfortable, and less bother. If both sashes move then at least one of the sashes can usually be induced to pin you to the cill. If you they don't both move, then you can't paint them properly anyway. I'll blame my father or the keen decorator down the road in Yeovil for giving me the idea it was a reasonable thing to do, but I doubt that H&S would be impressed.

Only something to try if within your comfort zone and at your own peril.

 

[Toby Newell]

This could be controversial.

If the sash windows are wide enough for a human bottom, they can be painted sitting on the cill, body out with legs inside. That's how I do my second floor windows. Granted anyone that sees it freaks out (a bonus), but as someone not keen on ladders at that sort of height, it doesn't feel overly precarious. Perhaps someone could hold onto legs, or something heavy could be found that legs could be hooked round, at least to start with. I have painted first floor windows that way in preference to working off a ladder as I find it more comfortable, and less bother. If both sashes move then at least one of the sashes can usually be induced to pin you to the cill. If you they don't both move, then you can't paint them properly anyway. I'll blame my father or the keen decorator down the road in Yeovil for giving me the idea it was a reasonable thing to do, but I doubt that H&S would be impressed.

Only something to try if within your comfort zone and at your own peril.

You do what you want. As a tradesperson I am not sure you would ever get insurance. You can get arrest anchors that fit internally. Still not sure you could paint a large sash window sitting on your bottom.

 

[Willsa]

Ye oldies! People talk on here about "sand back to wood" as if it's the vintage times still and one is sanding weathered linseed or lead.

The "sand back" ended with the advance of thick, gloopy layers of horrible oil gloss. As you can tell, I hate the stuff. It has no place anywhere (including indoors) these days. It firmly belongs somewhere in the Midcentury, though the competition for The Shiniest Paint Ever seemed rife until the 2000s.

Most people glossing something only manage to leave unsandable drips and their pubes stuck on woodwork for the posterity.

Burn the fecker, Burn!!! (The paint that is).

And.... Breathe. I'm fresh after burning various shades of green gloss off my stained glass front door and frame. Stinky, awful, inch-deep mess.

I'd actually go as far as to say that the heat gun is good for the wood. Kills bugs, fungus spores, makes the wood bitter and less-likely to be eaten, draws resins to the surface and naturally hardens and of course dries the old thing!

Cardboard cut-outs to the shape of the glass and then covered in reflective foil ensured the safety of the glass.

I'm going with Bedeck MSP.

 

[Toby Newell]

Ye oldies! People talk on here about "sand back to wood" as if it's the vintage times still and one is sanding weathered linseed or lead.

The "sand back" ended with the advance of thick, gloopy layers of horrible oil gloss. As you can tell, I hate the stuff. It has no place anywhere (including indoors) these days. It firmly belongs somewhere in the Midcentury, though the competition for The Shiniest Paint Ever seemed rife until the 2000s.

Most people glossing something only manage to leave unsandable drips and their pubes stuck on woodwork for the posterity.

Burn the fecker, Burn!!! (The paint that is).

And.... Breathe. I'm fresh after burning various shades of green gloss off my stained glass front door and frame. Stinky, awful, inch-deep mess.

I'd actually go as far as to say that the heat gun is good for the wood. Kills bugs, fungus spores, makes the wood bitter and less-likely to be eaten, draws resins to the surface and naturally hardens and of course dries the old thing!

Cardboard cut-outs to the shape of the glass and then covered in reflective foil ensured the safety of the glass.

I'm going with Bedeck MSP.

Oil gloss is 40% oil and simply an alkyd forming resin, just like linseed oil itself.

The only difference is more driers and siccatives.

Someone who knows what end to hold a nice Hamilton with eggshell or satinwood will get a much better finish than with a waterbased whose open time is measured in seconds.

And find a good apron...

 

[LadyArowana]

You do what you want. As a tradesperson I am not sure you would ever get insurance. You can get arrest anchors that fit internally. Still not sure you could paint a large sash window sitting on your bottom.

Compared to this, sitting on yer bottom seems much safer, possible cheaper too! https://www.bbc.co.uk/news/uk-england-somerset-23098040

 

[Toby Newell]

Not quite. Dulux is an old fashioned paint, so is less breathable than modern ones, but does claim to be microporous and gives a 10 year guarantee. So they will claim it’s breathable (‘microporous’), but it’s just not as good as others. About 30 years ago it was the best you could get (apart from specialist paints like linseed) but that was in the days of oil gloss.

So the problem, in much view, is not his choice of Dulux. It’s not the best, as we’ve all mentioned, and next time choose a different brand, but it should be fine on old windows for at least 5 years.

Your photos show catastrophic blistering, in selected locations. This is not the same as gradual cracking and peeling which is how you would expect the coating to fail after many years. So something has gone very wrong.

In my experience, there are two ways this could happen. It could be a reaction between the previous coating and the new coating. This is something the painter should have considered and tested, and if necessary sanded back to bare. BUT, if this were the cause I would expect similar symptoms all over, not just in the lower locations. It would also have happened within a day or so, not months later. So I don’t think this is the likely cause for those two reasons.

The other possibility is that he has applied the paint over wet wood, which has subsequently dried causing water vapour to be trapped behind the oil paint, causing blistering. Although Dulux claims breathability, this is when applied properly to dry wood. The areas where failure has occurred are those where rain settles and where paint weathers first. So these areas are most likely to have been cracked before painting and wet underneath, even if the wood appeared dry to touch. This is the only credible explanation that matches the degree of blistering, areas on the window of failure, and speed of occurrence. Looks to me like he rushed the job, not checking the wood dryness with a moisture gauge and not leaving sufficient time after sanding back for the wood beneath to dry before painting.

I’m not an expert, but neither is he. What I would expect of a professional is to apologise and promise to make good, and then for him to contact Dulux technical support to investigate the cause of the problem (though that is his problem, not yours).

I assume he offered a guarantee that the paint would last for a specific number of years? Even if not, you are entitled to expect a certain standard of workmanship and so have a legal claim, unless he specifically warned you in writing of a known issue before you agreed to proceed at your own risk.

On specific questions:
1). No, old wood is BETTER than new. It was grown slowly so has tighter growth rings and is more durable. The dryness comment is irrelevant. We’re recommending other brands only because they last twice as long and are better paints, NOT because you need a specialist paint for old wood. These are leading brands used by professional decorators. I was on a painters forum for 10 years and these were the ones they all used, never Dulux (which is for DIYers)
2) fair to ask for scaffold or tower. Few work from ladders anymore, for health and safety reasons. I would expect a pro to ask for that, even if expensive.
3) also sounds reasonable, but he should have sanded therefore.

Dulux was owned by Dupont who developed the first alkyd paint, ICI and now AkzoNobel, three of the top chemical companies in the world, ICI also owned Glidden which was known as a Dulux trade brand before Dulux trade and Glidden was sold by AkzoNobel to PPG. AkzoNobel is one of the most advanced coating manufacturers on the planet and Dulux make some of the best quality paints, a lot of painters use Dulux trade.

AkzoNobel also own Sikkens which make a broader and higher performance range of exterior coatings for wood.

Cheap pin moisture gauges tell you how wet the wood is at 2mm, useless, you need a professional gauge and drill pin or hooded hygrometer, actually you just need to strip and let dry.

If a paint is going to react, it doesnt need a day to do so, it will do so off the brush.

The issue is poor preparation, overcoating damaged paint or timber is always a risk, especially on a small island where conditions are likely to be harsher than normal.

Also, FYI as I stated before ALL paints are somewhat microporous and NO paints are totally microporous, also flexibility is important, which is probably partly why linseed paint is so good as it can take several years to fully dry!

 

[Stevers]

My decorating enthusiast neighbour in Yeovil was in the Crown Berger camp, and wouldn't use Dulux for anything. From 1990 to 2008 Akzo Nobel owned Crown Paints, that was until they bought Dulux, when they had to rid themselves of Crown via a management buyout due to monopoly concerns. Crown is now owned by Hempel Group. Paints have changed a lot in that time. I wonder if my neighbour stuck with Crown or Akzo Nobel through that modern corporate nonsense!

As an aside I've found Sikkens Rubbol paints (Satura and Gloss) to be excellent on bare wood, but hopeless over International Ranch Paint - supporting something that Toby Newell posted earlier about potential paint reactions. I'm big on prep, but not prepared to go back to bare wood every time I dolly things up, so my search for something that I can overpaint with continues. So far the Zinsser All Coat solvent based paint that claims to be 'vapour permeable' - though I have learned that doesn't mean much - appears to be lasting well.

 

[malcolm]

I use linseed paint for everything. Nice and breathable and you never have to strip back to wood (apart from the first time when you do need to remove all the modern paint first).

I've found a heat gun to be the best way to remove old modern paint. A Bahco 665 stripping tool is handy too. While stripping the timber at the front of the house I noticed burning on the wood. Turned out this was due to a previous strip where they had used a blow torch.

 

[Toby Newell]

My decorating enthusiast neighbour in Yeovil was in the Crown Berger camp, and wouldn't use Dulux for anything. From 1990 to 2008 Akzo Nobel owned Crown Paints, that was until they bought Dulux, when they had to rid themselves of Crown via a management buyout due to monopoly concerns. Crown is now owned by Hempel Group. Paints have changed a lot in that time. I wonder if my neighbour stuck with Crown or Akzo Nobel through that modern corporate nonsense!

As an aside I've found Sikkens Rubbol paints (Satura and Gloss) to be excellent on bare wood, but hopeless over International Ranch Paint - supporting something that Toby Newell posted earlier about potential paint reactions. I'm big on prep, but not prepared to go back to bare wood every time I dolly things up, so my search for something that I can overpaint with continues. So far the Zinsser All Coat solvent based paint that claims to be 'vapour permeable' - though I have learned that doesn't mean much - appears to be lasting well.

Sikkens make great products and yes! I did a whole years study on finishing preparation and many more since practically! It's all about adhesion... and curing, but mostly adhesion. It's difficult these days, as often companies will not tell you what their product is made of! You often have to read the TDS and SDS and try and work it out. A good clean and very thorough mechanical key is essential, in general most finishes do not like going on top of oil finishes, one should remember many alkyd based finishes and especially traditional linseed ones can take years to fully cure.

As a very important aside, in general I only use products I understand at a fundamental level, and that means phone the technical department, if I know more than they do then I steer clear! I have just spent an hour for example talking to Bona this week.

Someone like Ingleby paints should be able to talk to you at length how their finishes are made, why they are made like that and how they work at a molecular level. Sounds extra but it really isn't! Finishing seems like a dark art sometimes because you spend dozens of hours preparing only for to fall at the final furlong and that is normally incompatability when overcoating or coating conditions.

 

[Toby Newell]

and actually, despite my great-great-great-great-Grandfather, great-great-great-Grandfather, great-great-Grandfather, being painters and my great-Grandfather and Grandfather being decorative painters and French polishers, I am mainly a wood finisher, however, finishers are normally very set in their ways! Once you know a product that works you tend to stick with it... until of course, as you say, the company gets sold and the new owners change the formulation and sometimes you have to look for a new one! Sometimes you have to test and go back! It is a constant struggle, especially these days with changing environmental standards. I am sure most people are not aware that whatever the paint they have been using (mainstream paint) if they have been using that product for say 15 years, then it has probably undergone many changes in formulation during that time. What you often find is that the final end result aesthetics and durability are often similar between brands but it is the application characteristics that differ, and for a professional those are pre-eminent.

I still use some finishes that haven't changed in 30 years, because they work! Finishing can be a cruel mistress, you do everything perfect and for some unknown reason it doesn't work out. I would say trusting a finish is one of the most important things, so I fully understand people being in different brand camps, rightly or wrongly, it actually makes more sense than Apple vs PC for example.

I mean it's ok if it's your own house, but what if someone paid you to paint an entire house? Would you risk testing a new product? What if it went wrong? These are the issues! And FYI if I ever find the warketing manker who coined the phrase 'it does exactly what it says on the tin' I will personally shoot them as it is diametrically opposed to the truth. On almost zero occassions does the product do what it says on the tin and on almost zero ocxasions must you apply it how they describe on the tin! If they explained exactly how to apply a finish on the tin everyone would put it down and buy an 'easier' product.

I sometimes get professional trade products for my clients and they say 'but there are no instructions!' and I say 'exactly!' you are supposed to have some background knowledge then work out how to apply them by experimentation.

Try getting this past a marketing department! Which is basically the unwritten instructions to most wood finishes, DIY or professional. Would you buy this product?

APPLICATION INSTRUCTIONS: Shake and / or stir the product for 30 to 60 seconds. Make sure surface is clean, smooth and free from oil, wax or grease. You will probably need from three to seven coats depending upon the substrate porosity and level of build required. Drying times will be in the range of one to six hours depending upon timber porosity, ambient temperature or humidity, in rare cases this can be up to twelve hours. Intercoat sanding should be undertaken with P150 to P320 grit abrasive if desired but is not required if overcoating takes place within 48 hours. If you are overcoating an existing finish make sure to thoroughly key the surface, do a test sample and conduct a coin scratch test after 24hrs. Coating when too hot, too cold or too humid can affect the finish. When overcoating existing finishes or previously stripped surfaces there may be pervasive contaminants like oil or silicones. If you experience cissing, orange peel, lack of flow, or loss of adhesion, remove coating, apply barrier seal and / or add flow agent to the coating medium. White patches or failure to cure may be caused by bleaching agents or caustic chemicals in the substrate. Strip clean and try a different finish. Best of luck.

 

[IOW]

Hi, Thanks for all the info above which I have emailed my thoughts to my project manager who recomended the painter. Im finally having a meeting on Monday with the painter and my project manager/surveyor about the windows and how to move forward. I spoke to Bedec technition like a few of you mentioned, but he actually said for me NOT to use his product on the old sash windows as he said his product is not oil based and I might have problems when you open and close windows. They might stick. He said a better product would be a more oil based. So obviously I’m confused now. I know a few of you have mentioned stripping all paint off windows which obviously is needed. My project manager mentioned removing the sash and getting them belt sanded. I would like to hear your thoughts on the above. Cheers

 

[Stevers]

The sash windows on my 1879 house are original to the house, and I serviced all the windows with new sash cords etc. in 1997 after moving in. When painting I strip all loose and flaking paint, and treat bare wood with clear solvent preservative. I always paint the windows in situ - on the upper floors (somewhat controversially) sitting on the cills - legs in, body out. Back in about 2000 this was with International Ranch Paint - a self priming solvent based satin paint. I apply three coats on bare wood and two on sound paint, and apart from revisiting the cills a few years ago the Ranch Paint is still on there.

Counterintuitively the part of the sash hidden in the grooves doesn't need paint, and sashes won't suffer in any way because of a lack of paint there, in reality the enemy of sashes is too many thick coats of paint gumming them up. I paint the outside frame and the lower half of the grooves and all of the cill when doing the outside. The bottom of the lower sash I generally do with the inside to reduce the chances of it sticking - it does need to be in good nick as water ponds there. I move both sashes up and down (and side to side) to get to everything I need to paint, there being no stops on my sashes. It pays to do that in a logical order, and needless to say to do as much as you can from inside. On the outside we don't change colours and only paint what needs painting each year.

Preparation is 80% of the job, so clean, rough up/flat down and clean again. Any filling will be done with a two part epoxy filler (and epoxy hardener if required) and I now use 3C products for that.

It seems the EU solvent regs. did for Ranch Paint, and I've now changed to Zinsser All Coat solvent based, and that's what I'll be using this year (slightly thinned) when I go round them. Because we no longer have a proper window cleaner with a ladder, I'll also be changing any broken putty fillets (that's most of the bottom ones) to Timba Glaze.

For paint stripping on my bargeboards I used a Norton Rapid stripping wheel in an angle grinder for the first time last year. With the sashes out definitely the way to go - brilliant tool, but don't put it anywhere near any glass!
https://www.wickes.co.uk/Norton-Rap...g-Disc-for-Paint-and-Varnish---115mm/p/253224