Telos wrote:Well, I'll have to admit that I only have experience with new frames or refurbishing modern (less than 20 years old) frames. So, a 100 year old sash would be an unknown to me. However, I have seen a city wide project that involved Sikkens creating specially produced modern colours to recreate the original look of a series of very old buildings which were being renovated, one of which dates from 1556, the rest from late 1700's and early 1800's. The colour of linseed paints were carefully matched and recreated using modern techniques and modern paint technology. So, I know it is possible!
That's just matching the colours? Not the problem - I'm bothered about matching the durability, even if it's the wrong colour
What I would advise is only use professional grade paint and primer. The primer should preferably also be coloured to match the top coat. (This stops differential expansion, which can cause adhesion failure.)
Right. So grey Aluminium primer no good under anything but grey? Sticks well itself, except to putty. Have tried white oil primers - and white quick drying water based primers which are absolutely the worst.
The wood must be perfectly clean and dry, not painted in direct sunlight or when there is moisture in the air. So, no early mornings after September and don't start later than about 16:00 either. The paint will absorb moisture and lose its gloss and shorten its life.
Ideally, if it's a new build, the frames should be primed before installation with a "open" primer that lets moisture out, but protects from rain if it's left standing around.
However, I would say the reason for most external paint breakdown in modern houses is poorly painted internal surfaces, combined with poorly ventilated housing, retaining far too much moisture indoors.
If the outside surface is hermetically sealed and moisture from indoors finds its way into the frame, instead of out through the cracks that old windows used to have. Then the modern paint will appear to be crap, as the moisture in the wood drives the paint off. When in actual fact it is merely the way we live in draft free houses, sometimes combined with the wrong paints being used internally that causes premature paint failure.
I don't think I can repeat this enough, the internal paint finish is, in some respects, more important for the frame life than the external.
That's interesting. I'll think about it. At the mo I've got new repro windows with linseed oil paint outside and no paint at all inside - I coudn't get at both sides whilst it was on the gantry (big window).