MDF help

Hello all,

I'm working a heavy-duty shelving unit made of MDF and have gotten to the finishing stage. As far as I can tell my two options are 1) varnish, sand, varnish, or 2) acrylic base coat, sand, acrylic paint. In terms of MDF, which of these would you recommend ?

I would like to point out that I am in France, where there is apparently no such thing as an MDF-specific primer, and where MDF is rarely used in general.

Ideally I'd like to finish the shelves in white, though I suppose I could go with the natural varnished MDF color if necessary. My impression is that tinted varnish wouldn't work so well on MDF, an argument in favor of acrylic ?

Also, should I sand before applying anything, or just in between coats ? By hand or with a sander ?

If I go with varnish, I assume this needs no primer of any sort ?

Thanks for your wise advice.

Hi Tina

I'm no expert, but MDF absorbs a lot of whatever finish you use. I would use a normal acrylic primer or a sanding sealer and then finish with acrylic paint. Just remember that MDF is hard to finish well and sanding tends to make it go furry rather than smooth. Make sure you finish working it well before you apply the base coat as any imperfection (like screw holes etc) will shop up vividly on the painted surface. Painting doesn't hide a thing!

Hope the riot problems you are having are improving!

Cheers

Trav

Tina, Bonjour! I made a couple of shelving units out of MDF recently. If you can, give the visible edges a final sand using fine grit paper (100 or 120) on an orbital sander. Just a quick "polish" with this makes all the difference. I sprayed them with enamel, oil-based undercoat... light hand sand, then two coats of semi-gloss enamel with a light hand sand between... I was pretty happy with the result and it is hard-wearing. Good-luck MurrayD

I don't know if this will be much help to you as I know you are doing a large project, and it would be a difficult way of finishing something large, but just in case it helps.........

This is 6mm MDF which I cut with a coping saw. I stumbled across this finish while experimenting with stain on MDF. I used a Wattyl wood Gel in "Western Jarrah" and when I applied the first stroke with a rag, I got this lovely wood grain effect, you have to be careful though as it drys really quick, and you can only adjust it while it is very wet, you also need to be careful to do nice long strokes, as anytime you stop you get a puffy "sponged" look, which should be avoided.
I don't recall if I laquered it after or not? Most likely I would have.......

Hope this helps someone......
Ratbag

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Originally Posted by tinatina

Hello all,

I'm working a heavy-duty shelving unit made of MDF and have gotten to the finishing stage. As far as I can tell my two options are 1) varnish, sand, varnish, or 2) acrylic base coat, sand, acrylic paint. In terms of MDF, which of these would you recommend ?

I would like to point out that I am in France, where there is apparently no such thing as an MDF-specific primer, and where MDF is rarely used in general.

Ideally I'd like to finish the shelves in white, though I suppose I could go with the natural varnished MDF color if necessary. My impression is that tinted varnish wouldn't work so well on MDF, an argument in favor of acrylic ?

Also, should I sand before applying anything, or just in between coats ? By hand or with a sander ?

If I go with varnish, I assume this needs no primer of any sort ?

Thanks for your wise advice.

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G'day Tina
I recently built a bookshelf out of MDF (never again!) and finished it with semi-gloss white acrylic (British Paints from memory).
First tip: DO NOT sand before first coat (furry MDF is a bu.gger to fix).
Second tip: A good quality undercoat sealer IS recommended.
Third tip: only a very light sand is required (180 grit or finer) between coats.
Fourth tip: For a nice edge finish it is worthwhile using solid timber as edging because you will find it hard to get a smooth finish which matches the shelving because the exposed cut edges will stay furry whatever you do. Also if you decide to add real timber edging you can use a high gloss finish on the finished article.
Fifth tip (and most important): Next time build your furniture out of real timber..it's safer and more solid.

Cheers :D

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Originally Posted by Ratbag Oz

Hope this helps someone...... Ratbag

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That's a nice sized fish that you almost caught there Ratty. :U I like the faux timber finish on the mdf.

Here's a zincalume down pipe partially concealed by a radiata dummy post. I painted it cream and then stained it all with Cabots teak varnish stain. The downpipe is on the right, and looks more like timber than the crapiarta next to it:

http://i7.photobucket.com/albums/y26...ske/th_aax.jpg

And here's an mdf benchtop and doors that I built and stained, then pollyd a while back now. It's got a few scratches and it's looking quite dull now, but it hasn't been touched in ten years.

http://i7.photobucket.com/albums/y26...ske/th_aac.jpg http://i7.photobucket.com/albums/y26...ske/th_aab.jpg http://i7.photobucket.com/albums/y26...ske/th_aaa.jpg http://i7.photobucket.com/albums/y26...ke/th_aa-1.jpg

edit: Needs a good wipe down as well. Lots of dust all over it even though I gave it a quick wipe down before taking the pics. I might go over it with some steel wool and throw another coat of polly on it to give it a bit more life.

Contrary to some folks belief, MDF does in fact take stain and lacquer quite well I made a filing cabinet some 10 years ago and because of the height of the front of the drawers, could not find natural timber in the size I wanted so I used MDF and stained it in walnut and lacquered it to match the rest of the carcase of the project and it came up really well. You wouldn't pick it from timber to look at. I was going to post a picture but can't find my dam camera. Anyway it still looks good today after all that time.

I have seen in Bunnings a graining tool that you can actually crate a grainy effect in the stain to make it appear even more like timber. I haven't tried that but the idea seems good. The edges might be a problem but if that was my project, for shelving I would edge the MDF with a timber moulding.

Found it (the camera I mean) :) The fronts of these drawers are MDF

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Originally Posted by munruben

The edges might be a problem but if that was my project, for shelving I would edge the MDF with a timber moulding.

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The edges came up well on my top in the post above. It just takes a bit of sanding prior to, and in between coats.
I used 18mm and doubled it around the edges before hitting it with an ogee bit.

edit: Just saw your pics.
That looks like an antique John. :2tsup:

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Originally Posted by pawnhead

The edges came up well on my top in the post above. It just takes a bit of sanding prior to, and in between coats.
I used 18mm and doubled it around the edges before hitting it with an ogee bit.

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So you did, Sorry John I missed that bit, was more interested in looking at your pics.:):2tsup:

The pro cabinet makers use a 2 pack poly on mdf doors, any colour you like comes up a treat.

regards pal

I recently built a large built in wall unit from MDF. I edged it with hardwood both for the edges effect and to stiffen the shelves (necessary because the shelves would have exceeded the recommended span for MDF without bending with the intended load (books).

Two coats of Zinser shellac based primer/undercoat then sprayed with two coats of enamel. Once you have the shellac based primer undercoat you can paint it with any paint.

If you are leaving a "natural" mdf edge you can size the edges with diluted PVA before sanding them. Then proceed as before.

I recently finished this desk in MDF and spray painted it with water based gloss.

That looks great mailee.
I'll be doing my kitchen some time soon and I was thinking of profiling mdf doors for a gloss finish.
How are the edges done, and what sort of spray gun?

Thanks John, I didn't paint any of the edges as such as they are all banded with Pine. I would however give the edges an extra coat of MDF sealer and rub it down lightly with a fine grade. I used a HVLP spray gun to apply the finish although the MDF primer was given two coats with a foam roller before sanding down with 320 grit. Final finish was wet sanded with 800 wet n dry and then machine polished for the high gloss. :wink: