How to Spray paint MDF edges? Not working :(

[graham.murfett]

Gday all.
I'm resizing a customer's kitchen cabinet door after installing shelves for new ovens.
Original finish on door is 2-pack (?) gloss over MDF.
I am using British Paints Rapid Dry full gloss oil enamel to refinish. A product I have success with.
New cut edges soak up lots of paint.
Should I have primed?
What have I not done?
Can someone here who uses MDF give me some hints?
I am not a fan of MDF.

[Simplicity]

I've had a few clients MDF jobs professionally sprayed painted.

I'm un sure tho what primers they use especially on the raw edges.
But I did hear once about using plaster on the raw edge first???
But this is un tried by me and just hear say.
Tho it would seem to work.

Cheers Matt

[PJM16]

Primer is a must on mdf, like yourself I don't like using the stuff.
I'm not really sure what primer you'll need, but speak to the people at a paint shop and they'll be able to tell you what to use.

[Enfield Guy]

I seal the cut edges with a water based filler such as timbermate. Thin it a bit, a little bit them rub onto the cut edges including any roundovers. Allow to dry, light sand, prime, paint.

A lot of spray can products out there now say they do not require primer. I am dubious of the claim my self.

Cheers

[KBs PensNmore]

You must use an undercoat primer filler, a three in one product. To spray paint the edges, lay them flat on a sheet of MDF or what ever is handy, for small pieces, I use carpet edging with the little spikes on them, keeps the bottom off the surface and prevents sticking to the board. DAMHIKT. I apply 2 coats, turn over and do the same again, and then sand the edges and flats with about 240 grit paper. Then finish coating with whatever is required. I do about 90 pieces at a time 170 X 200 mm with rounded edges.
Hope this helps,
Kryn

[graham.murfett]

Thanks guys.
I have timbermate and 3-in-1 primers, both oil based and acrylic.
I presume to use oil-based primer on MDF!?
I still don't like MDF.
It cuts and shapes well, but that's all it's got going for it as far as I'm concerned.
But, we don't always get to choose

[KBs PensNmore]

Graham, the one I use is water based, can recoat after 2 hours, which suits me fine. I tried oil based, but having to wait 24 hr to recoat isn't for me.
Kryn

[malb]

Simple trick is to fill the edge pores with plasterboard topcoat skim, allow to dry, and sand back to flush and break the edge to the surface. This will result in a super smooth edge without a sharp corner, so the paint will wrap around evenly and stay there. Truly sharp corners and paint don't well and are prone to chipping. High build auto primer may produce a similar result, but can sometimes need a couple of coats to be truly effective.

[woodPixel]

I do lots of MDF. Lots and lots. Lots and lots and lots!

As said by others above, I believe these are the most effective:

-- automotive body filler with hardener. Sand it when it's "green"
-- timbermate, in pine colour. It dries very fast and can be redone in under 15 minutes
-- Haynes TriCoat

With the Haynes, use a mist coat, light sand, another light mist coat, light sand, then spray as normal.

All these will give you perfect results. The first two can be put on with your finger.

I had inferior results from other methods such as: plaster board filler, diluted PVA glue brushed on, shellac and tiling grout.

The above list is in order of effectiveness. From a practical and speed perspective the Timbermate is the winner. One would finish with Haymes anyway, but I included it as you might not want the others cost.

[Dirk_Pittwater]

I'm the same with woodPixel here!

I use loads of mdf all day everyday!

I also have a spray booth and we spray polyurethane for most of our joinery and other joiners and cabinetmakers and the rest of our work is finish hand painted on-site by painters.

We use a high build polyester undercoat. Easy to sand and sticks like you know what to a blanket!
We sand all our panels with 180g first then apply the undercoat then finish sand with 320g
Then we apply the topcoat or it gets installed ready for the painter to finish it off.

The odd occasion where I have had a panel needing to be cut down and painted again on site I use B.I.N - 3 in 1 primer. Can use any type of topcoat and it is easy to brush, roll, spray on or apply any other way you'd like to.

Very rarely have I ever put topcoat poly straight on a raw edge of a single piece. It does work but it's not the way it should be done. In this instance you would have to sand the panel to 500 or 600g and then apply the topcoat.

I have seen a few spray painters that do this all day to save them time and money but you get what you pay for.

Hope this helps.

Cheers
Dirk

[woodPixel]

Dirk, what brand poly undercoat do you use? I'm always keen to try new stuff.

i went down the automotive primer/under route for a while but I disliked the cleanup.

The haymes ended up as a default as well could get excellent results real fast. It's water based, dries quickly, likes to mist when diluted a bit and the binders really hold well onto nibs and fluffier. After 15 minutes I can sand with confidence. The only hassle I have is I like to spray a little wet than most and it doesn't like that. It fisheyes sometimes on hot days and that gives me the . Also, on days where it gets cold fast it tends to dew up easily, which in Canberra happens a lot in Autumn and Spring.

it sounds a bit negative, but these are just observations, easy to get around, plus I'm a bit lazy and like to leave things for bit after I spray

if you don't want to go public, please do PM me, I'm terribly interested.

edit: I've been thinking of trying BCcoatings PE230 for a while....

I must say, the soul who does not prime an edge of MDF is looking for a world of pain.

[Dirk_Pittwater]

Yer the bc coatings undercoats are good too. We used them for years. The polyester stuff is higher build and a bit easier to sand. All makes a difference when you have to do it all day everyday (about 20m2 undercoating everyday). Not so much if it's a few pieces here or there.
Pm sent.