Mdf

[Redback]

Hi All,
I am about to start building a low lying cabinet that will go in my home theatre. I have a projector system, so all it will hold will be the receiver, set top box dvd player and the sub woofer.

Anyways, to go with the look of the room, the wife wants it black. I therefore decided not to waste money on decent wood and assumed MDF will be best.

As I am new to this business and havent worked with MDF, what is the best kind of finish (oil or water based paints....I assume oil). Is it best to use one of those foam type rollers you use for applying oil paints to doors, or a low nap roller or by brush?. Do you need to prep the service with anything beofre painting?, is there anything I should do to the paint afterwards?

I am looking for a sort of flat finishe, not shiny or glossy.

Also, is it good enough to route a decorative edge to the mdf and then paint over, or would I need to attach a pine edging.

Thanks

RB

[simon c]

It's very hard to paint the edge of mdf as it soaks up paint so an edging would be a good idea. Another option is not to paint the edge but to buy black iron on edging.

If you do want to paint it, you will have to seal it. WhiteKnight sell an mdf primer or alternatively you can seal the edges with diluted wood glue - search this forum for hints as this aspect has been covered before.

If you want a low sheen finish, you may as well stick with water based paint - quicker drying.

[beejay1]

As stated, you should seal the mdf first. Ive found i get better finish on mdf by using those mini rollers foam type rather than the fluffy ones, and you will probably need 2/3 coats as mdf is very absorbent.

you might want to consider blackboard paint for the finish it works well.
By the way use proper mdf sealer
beejay1

[soundman]

You can get a good finish on MDF without too much trouble even on the end grain. I have had good success myself in the past.

You need to use some sort of sealer or undercoat that fills & sands well. I have found that there are much better things to seal end grain than PVA.

Machine your edges as clean as possible & give them a good sand with 120 grit.
Take your chosen sealer and give the edges a good coat, let it soak in a little & give them another. Let dry till sandable.
Sand the edges with 120 again then do your flats with 120 on a random orbit.
Give the whole thing a good seal coat starting with the edges first. Let it dry till sandable.
Sand again with 120 then 240 or further if you are keen, Then go with your top coats

I have had good results with black paving paint such as jet dry or permopave using estipol sanding sealer. They are all polyeurathane, forget they are a paving paint & treat them like a varnish or laquer & you will be surprise with the result. Jet dry black comes in gloss and satin, make sure you get the satin.
The result is very hard wearing. Works with brush or better spray. If brussing make sure the coats are wet & flowing (but not dripping)
I've done some office desks ( sprayed ) with it & cut the surface with wet & dry Followed by a rub with wax, peolple think its laquer.

Automotive undercoat with GMH flat black over works well too. GMH flat black is a cheap nitrocelulose laquer, you'll get 4 coats on in a day with this combination but you have to spray.

[Trav]

Soundman - good advice. I'm thinking about doing something similar too (but white, not black).

Can you/anyone else just confirm if I have got this right?

1. machine the MDF as needed and sand to 120
2. use an MDF sealer to seal the ends only (2 coats)
3. hand sand the edges and then ROS the main surface to 120
4. use the MDF sealer to coat the whole bang lot
5. sand the whole lot with 120 then 240
6. then top coats
7. then some kind of varnish or lacquer, cut back with wet and dry
8. then wax?

Absolute painting novice question - in the absence of a proper spray kit, am I better off using an aerosol can of the paint and varnish or using one of those foam rollers?

Cheers

Trav

Sorry to hijack your thread redback!

[echnidna]

Trav,
As you are painting solid color you shouldn't need to sand any finer than 120.
I wouldn't wax as this complicates future refinishing.
Aerosol spray packs are ok for finish coats except that you are generally limited to full gloss though black is available as a matte finish also. Gloss can be dulled with steel wool.
The Grey primer in aerosol cans is a good MDF sealer.

[Trav]

If I'm after a really glossy, shiny finish, I was thinking of using a gloss colour coat, and then cover with a few coats of spray varnish/lacquer over the top to build up the depth of the finish. Does that sound like a logical process?

Do I need to rub each coat of varnish back before spraying the next?

Cheers

Trav

[echnidna]

"Do I need to rub each coat of varnish back before spraying the next?"

Only sand enough to denib the previous coat. Eventually it will all build up to a stage where you have a fine finish without using a clear (which may yellow over time)

[Redback]

no probs hijacking the thread....

Its useful information for me too!.

Thanks for the replies everyone. Most helpful

[Shane Watson]

Hijacking the thread? Nah that ain't hijaking as no one has mentioned pancakes yet!

Soundman is about spot on, and he should be as as I understand it he paints this stuff quite regularly.

I did paint the stuff commercially for over 10yrs but that was with 2 part poly-u off the gun full gloss no imperfections and I don't mind sharing that several awards were recieved

And yeah its damn easy to paint. Just basically follow soundmans advice. Experiment on some scrap if your unsure.

Cheers!

[soundman]

The old jet dry is viable with a brush (if your good) but I've never used their white.

White anything is a chalenge because of opacity problems so you will need to use a white primer.

A mate & I are just starting to do some experiments with RECINE " ENAMACRIL" & related products & its looking very good.

It is a water bourne acrilic enamel substitute. The primer has good build & leveling and sands well. The top coats seem to level quite well. the products all dry reasonably quick and go off hard & properly.
The mate has done some spray samples on burch ply & it comes up very well better than spraying enamel but not quite as nice al laquer.

As usual I'm trying some realy weird applications but the product is looking impressive. And there is hardy any smell.