Scuff X - Crap Finish, unsure what I did wrong?

[User1234567890]

I have fitted a new MDF MR, pre primed window sill. The existing white primer had taken a battering during the install, and there were some bare MDF ends that I had shaped. I used a couple of generous coats of Zinsser BIN (which was a right ball ache to apply) filled in-between coats with Toupret fine surface filler, and then sanded it back to a lovely flat finish. I noticed that there were still some darker patches of the MDF showing through, so did another coat of BIN but they were still showing, so I sanded that flat, and I gave it a couple of coats of Leyland Acrylic primer undercoat and that fixed the dark patches. I then sanded that flat, and it looked and felt really good.

So, today, the temps were only 17/18c, so I thought I'd have a crack at applying the scuff x satin. I thinned it 5% with the BM extender, mainly to give me a bit more time to get it on and smoothed, but I also read that it helps it to flow and level out.

Mini microfibre roller and clean tray. Roller, fully de-fluffed with sticky tape. Brand new dampened Wooster gold tip 2" brush for laying off. I've used these brushes before and I managed a good finish. Scuff X Satin, Super White.

Stirred the Scuff X thoroughly, added some to a big, clean paper cup, and mixed in the BM extender thoroughly, added some to the roller tray.

Applied with the mini roller, layed off with the soft brush. I noticed quickly that it got really sticky, really quickly. Working fast, and getting it on, meant that laying it off was no more than 30 seconds after rolling, and I was able to smooth it in one pass, but going back for a second pass would usually mean that the brush would stick/drag and it would leave horrible sticky marks. Even with the extender, and relatively cool temps, this was drying as quick, if not quicker than zinsser bin.

So I did one coat, and it is terrible, it hasn't really levelled at all, and the brush marks are enormous. It'll need sanding off and starting again. It has also micro bubbled around some of the toupret fine surface fillered areas, despite them having several coats of primer on them. Gutted.

Does anyone have any top tips for applying water based paint to woodwork without having brush marks? Everything, everywhere that I'd read about this paint, said that it doesn't leave brush marks and looks close to a spray finish. Got to be something I'm doing wrong?

 

[Wayners]

I think the heat got you. Been to hot...

This is how I'd do it.

I'd mask the uPVC with Masq low tack and any wall areas.
Roll surface right to the edges. You might need to tickle the edges with a brush then roll over tight to the edges.
Your messing with it when you shouldn't. It's going a bit jelly like. It could be the heat as 25c it getting to the point the paint will start to play up. Paint likes room temperature so 20c.

You need to get a good coat on as people tend to brush out paint, but you need enough on so it levels. Hard to say if you got that wrong...
If you want to know the paint depth pick up a wet comb. Random link. Probably cheaper elsewhere https://amzn.eu/d/dI2dLAc
Read data sheet for depth guide for paint and have a play as you maybe shocked what you find.
Those bubbles are from filler sandwiched in paints.

I'd of given MDF 180 grade sand then one BIN with a foam roller. It's thin. No opacity. That's how it is..... Just get an even thin coat on and leave overnight.
One acrylic primer then your ready mixed filler.
Light 320 grade sand.
Another acrylic primer.
Leave overnight.
320 grade light rub to denib primer.
Damp microfibre cloth.
6am to 7am when it's cool use a Uni-Pro High Tech Micro-Fibre 6.5" 4mm Nap roller and get a good coat of scuff-x on. Pull tape when paint is wet.
Leave it. Walk away.