Thread: 2 pack finish on MDF

First step get the primer smooth. If you brushed or rolled it on and you have marks you will need to let it dry and sand it smooth. MDF has a waxy surface and can cause drying problems with some paints which melt the wax and then the wax prevents the paint (primer ) dry evenly.

Your finish will never be better than the surface you paint over as the paint follows the ups and downs of the surface) If it is a slight difference then a wet coat of enamel may flow out flat and smooth but you run the risk of runs especially on vertical surfaces.


You havn't stated exactly which Dulux 2 pack paint paint you have, there are more than one all require different processes.

I am using Dulux Super enamel. I am getting a good smooth base with the primer. But getting the "orange Peel" finish when applying the enamel using a roller. Tried using a fine brush but still getting brush marks.

Sand, sand, sand. Might need to go down quite coarse to get it flat (180 or less), then work up through the grits 240, 320. Then give it another coat with a brush, work slowly and don't work the surface too much with the brush: let the finish flow slowly and smoothly onto the surface from the brush, say one stroke to cover each strip. Let dry completely, then sand lightly at 320. Then another coat. Then sand at 400. Then another coat. That should do it.

You confused us by stating that you were using 2 pack, thats paint which has a hardener in it.

A roller will give you a peel finish you need to use a brush but it must be a good quality pure bristle brush not a cheap one they have synthetic hair or horse hair mixed in with the pigs bristle to cheapen it.

A brand new brush may shed a few hairs so use it for the primer first or use it on something else to get rid of the loose hairs _ or pluck them out on your job as you go but that won't help with the smooth finish.

Obviously you have paint on the job already so do as Zenwood has suggested and sand it down smooth. Unfortunately if you have more than one coat on it may be still soft underneath and it may just glue your paper up. If that happened I would just wash it off and start again but you can wait till its drys but a thick sticky coat can take months to dry hard all the way through.

Once the surface is smooth get two containers one big one and one tin which will fit inside leaving about 25mm clearance around the sides. Boil some water and put it in the large one Put your paint straight from the paint tin without thinner (turps) into the water (watch there is not too much water or it will overflow into the paint tin.)

Let it sit for a few minutes the paint will get thin. Fill the brush apply to the surface and spread it all over the panel.

Wipe out the excess paint from the brush and lightly wipe along the surface in one direction smoothing out the paint and removing any excess. If necessary wipe out the excess paint from the brush and keep going . If its a vertical surface brush up and down not across.

Try to do it only once don't play with it. The enamel is slow drying to allow the enamel to flow out and loose the brush marks.

I was shown this by my old tech teacher when I painted my Model T Ford at Tech dark green. I was challenged several times by people who did not believe it was brushed it came out as good as spraying it.

You must have a good brush and ( i was lucky the teacher supplyed me with his old brush from the railways. )

Whenever you do something which matters test it first before you launch into the actual job saves a lot of mess ups. As you already have paint on the job one coat should be enough. Normally you only put on two coats of this paint anyway don't be tempted to put on more (unless you have a stuff upand then you will have to leave it longer to dry out ) extra paint will only cause worse problems such as the paint wrinkling.

Hot spraying - doing what I suggested heating the paint is a well known paint process, they make spray gun units which have a heater to heat and spray the paint. As the paint is not thinned the end coat is thicker on the job meaning you can get away with one coat. Something which may be necessary eg: painting something large like a bulldozer you can't climb back onto the dozer to put a second coat on as the first one is still wet.

Heating the paint gives a marked improvement on the final finish so much so that you can visually see the difference between paint thinned with solvent and thinned with heat.

I reckon by the sounds of it you are over working the paint... with enamel put it on thick(but not too thick...) and dont go back over it again after 5 minutes(once flowout stops)or so, as you will disturb the skin that forms.
Enamel applied properly with a brush can turn out as good as if not better than a modern cars paint.(especialy on mdf or metal)

Zen there shound be no need to sand MDF(in good condition), only the end grain when sealing should it be sanded. To get the equivalent finish of mdf's smoothness you would need to sand 1000g +.

I dont recon there is much point sanding past 240 gritt on enamel particularly if applied with brush or roller many would say 180 is far enough.

Have you thinned the paint. If it isn't thin enough it wont flow out, if its two thin it will run like buggery.

You will need to be liberal with getting the paint flowing off the brush without letting it runn. Enamel is a bastard..... yeh that looks nice & smooth & wet... turn around & 5 min later its runn all over the place.

You are realy drawing a long bow to get a smooth finish by any hand applied means... spraying would be soooo much easier.

Getting a realy smooth finish with enamel is posible but you realy have to have everything going for you.

Id be tossing up between the brush and a realy fine roller either way It will make man of you trying.
cheers

Soundy it probarly run all over the place because you have thinned it to much, even for spraying its only thinned no more than 10%.
There is no reason to thin enamel if applying with a brush or roller.

We use it extensively at work on hand rails, its slopped on thick as honey in freezing cold weather and it comes up mirrior shiney.

'Once the surface is smooth get two containers one big one and one tin which will fit inside leaving about 25mm clearance around the sides. Boil some water and put it in the large one Put your paint straight from the paint tin without thinner (turps) into the water (watch there is not too much water or it will overflow into the paint tin.)'

Durwood. Do I read this correctly. Are you saying pour the paint into the water or are you saying place the tin with the paint into the tin with the water

He's saying to make a crude double boiler, put the tin that contains the piant into the hot water.

Thanks Harry72
Boxers

Using water based acrylic (low gloss satin) was told it looks more classy lol, I found spraying a sealer/undercoat on unsanded mdf, then sanding with 320 grit garnet(I know) paper using orbital sander. Gave me a mirror like smooth as glass finish that made the topcoats orange peel slightly (on the shelves only).

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There is much contradiction about mdf reaction with oil based paints, ie Don't use this paint or that paint it will decay the mdf, you can only spray acrylic water based paint with an airless spray gun. (Hence my use of water based paint)

So after getting advice from 3 paint shops and 2 professional painters calling manufacturers
hotlines realised I was on my own.


(1) Whats the point sanding sealer/undercoat, when it comes off the gun feeling a little rough( isn't the idea of undercoat to provide a key for the paint)

(2) Yes you can use a compressor to apply water based paint. Long as there is a picture of normal spray gun on the paint can.( just not the 1st type of "do all " miracle paint I was sold)

(3) Thistle joinery in the uk , which make all their furniture from mdf. Advise all customers use oil based paints (pics below)

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(4) To be honest i think the undercoat after sanding(mdf), looked and felt a lot better than the top coats did. But because the piece needed that durable finish what could a man do lol.

(5) Floetrol acrylic paint conditioner is magic stuff when spraying, just as a test I touched up some endgrain areas with a brush... Impossible with my 20/20 vision to see where.

End result - get the paint on however you can and hope for the best.


HJ0 cheers