Spraying primer on to mdf

[tom46]

HI guys,

I make loads of cabinets from mdf and recently have had to start painting all of them. After having useless results with the earlex hv5500 spray gun i'm now using just a compressor and cheap gun (with much better results).

However the constance issue i have is with the primer. I finish the units in a dulux satinwood (water based) which is great. However if i spray a water based primer on all it does is fur the fibres up in the mdf which won't sand out. So i've had to result to rolling on oil based zinseer primer then spraying waterbased over that. However this is rather time consuming as i have so many large mdf units.
Would anyone know of a good primer/sealer which can be sprayed that doesn't fur all the fibres up.

Thanks Tom

 

[Jak147]

+1 would love to know the answer to this, i have had the exact same experience as the OP even went onto zinsser BIN as the base coat.... Doesn't it dry fast and how super smooth does it sand up

 

[jonny round boy]

Doesn't help with painting stuff you've already made, but I've found moisture-resistant MDF takes paint far, far better than standard. It costs slightly more, but it doesn't fur up & the time saved more than covers the extra cost.

I've stopped using standard MDF altogether - apart from the new computer desk I built for myself last week (just because I had some in stock that I wanted to use up!).

 

[AlexThePalex]

In my fathers' spraying business we sprayed thousands of MDF kitchen cabinets and other things like CD racks. We had a factory nextdoor and we did all their spraying.

It has been 20 years now, so I don't know anymore what paint we used exactly but it was a water based, very scratch resistant high solid paint/primer and we never had the problem you described. I think that the high solid paint and the high quality of the MDF they used were together responsible for a good result.   

 

[Jak147]

We to only ever use MR mdf but still have the same issue with the surface fibres, have all but given up on the sprayer now and left the painting to the decorater (Who is very good) but it's just not the same as a sprayer. Especially with more and more ppl using LED tape to light built in cupboards. nothing like a nice low angle raking light to show up every brush stroke!!

 

[jimbouk]

Use a pu or ac primer. Or a pre cat. Mylands morells or movac all supply these. They also now make a waterbased hi build primer. Not as good as the smelly stuff but better than basic. Always use the mr mdf. You will need a fully extracted and vented booth and possibly local authority permissio  tho.

 

[mastercabman]

I use a white vinyl primer (solvent based)
Goes on very smooth and sands really nice
But I don't know what you can get where you are
I guess you probably want to use a waterborne product
Using a waterborne/water based primer will raise grain or create that fur thing you're talking about
Primer and sealers usually need to be sanded before top coating
Is the furing happening on the flat surface?or is it just the edges?
With the edges I sand them up to 320 then prime ,sand again and another coat of primer
Works great for me
BTW I don't really like showing MDF edges
I usually add a piece of hardwood

 

[tjbnwi]

Zinnser Seal Coat for the first coat. Top with anything you want.

If you want to stay with water based, SWP Wall and Wood.

Tom

 

[SMJoinery]

Sorry to hear about your issues especially with the earlex system.
If it helps we also use the earlex hv5500 kit to spray all our builds including MDF and don't get a lot of what you describe.
The method used is...
MRMDF board.
2 coats of Leyland brand water based wood primer diluted with clean water and consistency checked with viscosity cup from earlex kit. We do have to lightly sand between coats but it's a "knock off" sand, not aggressive and 75% of the time done with the abrasive sponge pad things.
2 coats of Leyland brand water based wood finish again thinned to viscosity and a very light rub before final coat.
Some edges if exposed need a further pass but only if we haven't hit them just right with first few passes.
Using this method we can easily get 3 or 4 good costs on in a day to a small cabinet job as it dries very quickly (60-90 mins)
I must say I find the earlex quite really good for any water based spraying tasks we have undertaken so far.
Hope this helps.

 

[tom46]

HI,

Thanks for all the replies.

IN reply to master cabman yes the furring is actually worse on the flat surfaces, it comes up like a load of fibre flakes have been thrown into the paint.

I do use zinnser (oils) but am under the impression you can'r spray oil based? Is this correct?

Does the leyland water based primer not just soak up into the mdf? Or are you using a ms mdf to stop this slightly?

Thanks

 

[SMJoinery]

HI,

Thanks for all the replies.

IN reply to master cabman yes the furring is actually worse on the flat surfaces, it comes up like a load of fibre flakes have been thrown into the paint.

I do use zinnser (oils) but am under the impression you can'r spray oil based? Is this correct?

Does the leyland water based primer not just soak up into the mdf? Or are you using a ms mdf to stop this slightly?

Thanks

No, I wouldn't say it soaks up but yes with it being MR MDF it's not likely to. I find it covers fairly well with first coat but the boards green colour is still evident on edges. We just sand lightly and spray second coat which gets them sorted.
I wonder if most of the issues you are getting is the fact that it's standard MDF board and the watered down paint through the sprayer is furring up the board badly.
As an example, I get less furring after 1st coat of primer on MRMDF board face (not edges) than I do using same product and application on pine, meranti and poplar.

On a final point, I had a thought to experiment recently with MRMDF and took two pieces of board from same sheet, gave one of them the above standard four coats (primer, under and 2 finish) and did the other board as 4 coats of finish only. Sanding lightly only between coats.
Result was no real difference between finishes, not any less scratch resistant etc.

Hope that all helps.
Scott

 

[aas]

The guy who used to do my spraying, used a car body spray filler/primer, (you know the fairly thick stuff), for the first coat, then fine sand to remove all imperfections, before finishing coating 2 or 3 times.

 

[tom46]

Hi Scott,

Thanks for that i think the issue may be as i'm using standard mdf and not MR mdf. I did however after reading your post go out and buy leyland satin wood and found it much nicer to spray with rather then the dulux satinwood.
I also used a test piece and applied just four coats of the satinwood (no primer) it did still fur up like it does but cover very nicely. Will certainly be using leyland paint from now on. May try mr mdf next time too.

 

[Billedis]

to start off with, I am just a hobbyist, so what I might do may not work in a production shop.

I use drywall mud on all my mdf prior to spraying.  I just slather it on with a plastic trowel, and try to keep it as smooth as possible.  30 min after application I use 150 grit sandpaper in my RO125 to smooth it down.  Once that is done, a coat of primer and two coats of finish and I am done.  I always use Bri wax for the final application with 0000 steel wool and it turns out great for me.

Thanks, Bill

 

[SMJoinery]

Hi Scott,

Thanks for that i think the issue may be as i'm using standard mdf and not MR mdf. I did however after reading your post go out and buy leyland satin wood and found it much nicer to spray with rather then the dulux satinwood.
I also used a test piece and applied just four coats of the satinwood (no primer) it did still fur up like it does but cover very nicely. Will certainly be using leyland paint from now on. May try mr mdf next time too.

Your welcome, it's exactly what FOG is for and why I like it.
As another heads up we have used the same product with tints added to colour it.
Where we buy ours has the facility to tint and mix so we can pick any colour the client wants and have them tint it to suit.
I think they add eggshell tints to the satin wood product as that works best. We then dilute to viscosity and spray away.
We have also matched some Farrow and Ball Colours this way which is a popular brand up here in our area.
Got to recommend the MRMDF board though as its a much cleaner finish.
Good luck.
Scott

 

[Wuffles]

Leyland is the trade name of Johnstones (which is already Trade). I get prices in their shops on the Johnstones Acrylic Eggshell colour mix that make the staff cry and am more than happy to share them. They generally have a shop nearby but will also deliver for anything more than a couple of cans.

They once price matched another shop selling their own product after I threw a hissy fit about being able to buy their product cheaper elsewhere.

I get very good prices on the vinyl matt & acrylic matt too, not sure on satinwood but worth a punt.

No strings, just passing on the discount.

PM me if interested.

 

[tom46]

Yeah i did actually try the leyland which was much better then the dulux i'd been using. Then i needed a dark grey and they could only do that in john stone satinwood. However i got that and again that seemed even better then the leyland, well i got a better result with it anyway. [big grin]