Any tips for [water-based] glossing factory primed MDF Architrave?

Hey all,

I'm really struggling to paint my new architrave. It's pre-primed MDF from a timber merchant, the nice almost chalky primer, not the smooth stuff. I'm using Purdy Sprig brushes, so can't see that been the issue.

I have glued and screwed it, filled the holes, sanded smooth, shellac'd [Zinsser Bin] any bits of un-primed MDF, undercoated with decent acrylic primer/undercoat, de-nibbed with 180g, another coat of BIN on the bits that were exposed and full coat of primer/undercoat and then tried to apply a water based gloss.

First I tried Crown Trade fastflow quick dry gloss - and it was awful stuff, almost translucent, and on the MDF, it skinned over within about 10 seconds - too quick to do the inside edge, face and outside edge in one pass.

So, I scraped it off before it had cured, gave it a quick sand, and slapped on another coat of the primer/undercoat.

Then I tried again with Dulux Trade Quick Dry Gloss Paint, the internet seemed to suggest it is a decent water based gloss. It is much better; It gives me a full 30 secs before skinning over! Anyway, it has a good opacity and flows much nicer.

But in some places it still dries far to quick, and even just doing the inside edge and the face, in 4" sections, I'm leaving huge tramlines and lines between sections at best, and at worst, it's skinning over and sort of peeling off when I'm trying to lay of, getting an orange-skin like texture.

The same paint, over the same primer/undercoat goes on to pine skirting quite nicely, and leaves a really nice finish after two coats. A trial run on some [different] primed MDF of cuts also went on beautifully and dried brush-stroke free.

In the last year or so, I must have have painted 50+m of MDF skirting and architrave in a different part of the same house with a water-based satin wood, and shallow-tramlines aside, it went on just fine.

What am I doing wrong? I can usually work out these sorts of problems, but these 5 doorways are just killing me!

Whitling2k

 

OK cool - hadn't thought of that. Anything to stop that pesky skin forming. Do you think that will be OK on the MDF? Could it make it swell? I had almost thought of building up loads of single brush strokes, one streak, move an inch away, another streak - so alternate and slightly overlapping stripes... [joke!]

More seriously - I had thought about watering a sample of the paint down 10-15% and trying that.

 

he he!

 

Hey guys - thanks for all your tips - I sorted it in the end actually - by literally throwing on a really thin coat of the Dulux Trade WB gloss, which sealed the MDF, meaning the second coat went on really nicely - not too unlike a fast flow oil-based gloss.

Learnt a few things on the way too...

- Just leave mistakes! I'll cause more damage trying to even out a brush mark than just leaving it. Only one brush mark to lightly sand out between coats then.
- the first thin coat will leave brush-marks; the second thicker coat will not; they are mostly covered by the second cote.
- Accept some brush marks, it's the trade-off between drying time / smell vs. oil gloss.
- Wash the brush every 20 mins or so - keeping it damp, stopping paint drying on, and keeping flexibility.
- 400-800 grit rubdown on flat surfaces (not edges) between coats prevents crazing from gloss over gloss. The stuff is hard-sandable after ~ 48 hours.

Now I have got used to it, I'm actually quite impressed with the Dulux Trade - I'm still a crown fan for emulsion though!!