Just wondering if you use oil based as an undercoat and then say a water based stainwood over the top how much will this affect the topcoat, yellowing is my main quandry?

Has anyone done a sample and actually seen the timescales etc?

My oil based choice would be coverstain and then a w/b satin

Haven't tried this one yet, but I see where you're coming from. TBH, would have to say sticking to one of the better covering topcoats would hopefully minimise any yellowing shining through. Honest answer though -

I've also been wondering if hybrid paints may suffer from any yellowing. Farrow & Ball Estate Eggshell is the one that most readily springs to mind. Given that it's an alkyd/acrylic hybrid will there be any (delayed yellowing) God, this trade has turned complicated these days.

I recently did my porch with 2 Coverstains and then Dulux Trade Weathershield WB Gloss and its fine mate. I'm sure Dulux would advise against it but it was outside and I needed the first 2 coats to go off quick. Not sure whether it will yellow, I'd guess not as the top coat is WB but only time will tell I guess!You might need to give it 2 topcoats but apart from that crack on mate.

I've used Cover stain and 1-2-3 as an undercoat before acrylic top coat and to be honest I can't tell that there is any difference to the finish product apart from the 1 hour drying time. Personally I'd prefer the 1-2-3 simply because it's easier to clean up. As Pros can you tell me 'is there any difference' ?

Opppps this was meant to go into the previous thread by Fordy who asked about applying OB before WB top coat. -Sorry.

Morton. Do you mean this thread ?

advice-from-the-more-scientific-of-you-t52962.html

Hi yes, can you add it in please?

we've tested both acrylic and hybrid - 2 types.
Acrylic doesn't adhere as well as I would have liked but it does harden over a period of about 14 days. The adhesion is dramatically improved by sanding with a fine sandpaper.....no surprise there.
Hybrid adheres brilliantly - no issues at all. The F&B is fine and sticks very well even with minimal or no sanding. The Sikkens BL has its own solvent born primer undercoat which is superb. If not using the sikkens primer u/coat, I would definitely be thorough with sanding as it seems to have less adhesion to un-sanded precats and the like. The F&B is alkyd/acrylic, Sikkens is polyurethane/acrylic which gives you an indication of behaviour

If you put these hybrids in a room with no natural light they would yellow somewhat - but there is less of the resin in these products and also less yellowing of the binder materials so it will be reduced and I have yet to have seen evidence of yellowing myself but I would never offer guarantees if the conditions were likely to induce yellowing

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I have often done oil based unders and then water based (gloss) as a top coat...no problems at all..works great on radietors and the water based still white.

The situation aint really much different to painting over existing oil based finish with water based.

Using oil based undercoat always gives you a longer working time with the gloss and doesnt drag as much.

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The yellowing of the non-volatile longer chain Hydrocarbons in the undercoat should not show through the WB satin provided that you have not tried to one coat the satin, thus leaving it Opaque rather than white.

Consider this:- If you had undercoated a stain to seal it, and then emulsioned over it twice, it would have never yellowed through before because the yellowing in emulsion remains below the finish sheen. If the sheen didn't seal the surface, you would be able to wipe the trim with a rag with turps and make it whiter.

You are inventing things to worry about.

HBWT you should try that Sikkens oil based primer/u-coat, it is delicious

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Not inventing things to worry about just asking a question!

If the base/u/c coat is yellowing surely it must have some sort of effect on the top coat.

Not a great fan of w/b especially from bare wood.

Sometimes what may seem a stupid question is the most important!

Yes it's definitely a good question. Cannot work out Jozeffo's post apart from the fact the point - if you put a solid coat on it will cover even if it yellows. But a couple of coats of wb isn't solid. So from that perspective the question remains unanswered.

Try Mythic wb primer?????

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Hi PC, the solvent born primer you mentioned is this the water soluble one they recommend ? As it is indeed the daddy, and sets up lovely for the top coats, essential in my opinion to achieve the best poss finish, having tried acrylic u/c and 123 they just don't stand up to the BL primer in terms of obliteration and finish.

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That's good advice - the BL primer is quite similar to oil based. Go for Mythic if you are looking for opacity.

Both don't have much body and you have to blitz out fine textures with p240

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To err is human.

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Hi Puma , still to try the Mythic range .... Bertie will have me guts ...

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I wanna build my Rome and get high but i can't find my matches...