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Slow drying times - humidity problem.

Help with choosing the right coloured milkpaint to slather all over your new project.

Slow drying times - humidity problem.

Postby RogerM » 09 Jun 2016, 10:07

I've just refurbished my front door, and have finished it with one coat of Sadolin Ultra base coat and 2 coats of Sadolin Ultra Walnut. The can says touch dry in 4 - 6 hours, and re-coatable after 16 hgours, yet 24 hours after applying the top coat, it is still tacky, despite the outside temperature being 22 deg C, and having stirred the product to within an inch of its life.

I phoned the Sadolin technical help line and they told me the problem was caused by high humidity, and that has a far greater effect than temperature. In fact, I was told that a cool dry day (10 - 12 deg C)will produce quicker drying times than a hot (24 - 26 deg C) humid day. With the current high levels of humidity you might want to take this into account before applying a finish in the late afternoon in the expectation that it will be touch dry by nightfall.

I've also experienced the same problem with Sikkens in humid conditions.
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Re: Slow drying times - humidity problem.

Postby Rod » 09 Jun 2016, 10:36

That's interesting - I use Sikkens HLS and Filter 7 - generally in high summer and never experienced that - perhaps I've been lucky?

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Re: Slow drying times - humidity problem.

Postby RogerM » 09 Jun 2016, 11:44

Maybe relative humidity in darkest Hampshire is lower than in Devon Rod.

In fairness to Sadolin, their data sheet does state :-

Touch dry : 4-6 hours.
Recoatable : 16 hours.

Note: Drying times are dependent upon absorption of substrate and drying conditions. At low temperatures and / or conditions of high relative humidity, drying times will be extended.

Whilst Sikkens state no such warning, their data sheet does specify that the drying times quoted are for 20 deg C and relative humidity of 65%. I'd hazard a guess that RH is much higher than that at the moment.
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