Prep for painting MDF

[brittas2009]

Hi... We've made some MDF furniture and want to paint it... We're probably going to finish it with an eggshell but was after some priming advice. Should we be using Zinser BIN or is there something better for MDF?

I think it's going to be painted by hand, although a friend has offered me the use of an HVLP .... Not sure how to use it so may leave that for another project

Any advice would be much appreciated

Brittas

 

[opps]

DO NOT use BIN.

It is a wonderful product but a mare to sand back and you will not be able to get a good finish applying it because it dries too quickly.

If you are going down the HVLP route then the BEST finish will be using acid catalyst spray.

You will not need any primer. 3 or 4 coats will suffice, it is possible to apply them all in one day but I would recommend applying the first coat and leaving for half a day so that it is hard enough to sand back with 400g silicone carbide paper.

Find somewhere suitable to spray as there will be lots of smelly dry over spray and acid cat fumes are not nice. (outside will be fine if it is dry and not windy).

Morrells is one of the best places to get the stuff.

Acid cat dries so fast that you can pick the item up with in minutes of spraying..

My bread and butter is painting cabinets on site with acrylic primer and lots of sanding followed by oil eggshell. Were it not for the small and over spray I would do everything in acid cat.

 

[brittas2009]

Opps

Thanks for the advice.... This is all a new world to me, so just to clarify, If I were to go down the paint by hand route, it would need to be an acrylic primer followed by egghshell?

Thanks again

Brittas

 

[opps]

Yep

BUT the acrylic will raise the grain. I don't mind that because i have lots of very nice german sanders.

I have seen others say that the Zinsser 123 is very good as an acrylic primer, less grain raising and even good enough to use waterbased eggshell over. I haven't tried it yet though .

I currently use the crappy leyland acrylic primer, with lots of sandinig followed by two coats of dulux trade oil based eggshell

 

[joe-90]

The easiest way to get a good result is.

Oil Primer followed by oil undercoat. Sand it with a block and 120 grit until it is perfect. If it's not perfect do another undercoat. It sands easily and dries fast and has the really useful ability to fill imperfections. Sand again with about 320 grit.

Don't proceed past this point if the furniture is not perfect.

Then add a tiny amount of white spirit to your oil based topcoat - until it flows without dragging. Brush on and 'lay off'. Job done. Have a cuppa.

 

[opps]

If you sand it with 120g you will have no primer or undercoat left!?!?!

And the 2010 voc undercoat takes day to harden.

There is some validity to using oil based primer (it won't raise the grain for example), I just find that most of them do nothing for colour obliteration and take too long to harden. The last decent one i used was the Beckers stuff but you can't get their paints North of the river.

By the way, in between coats sanding should be done with stearate coated silicone carbide paper and not aluminium oxide.

The question of painting MDF is quite contentious and there are many favoured methods, some use the clear Rustins MDF primer, others use thinned varnish.

My preferred route is based on years of specialising in cabinet painting and is the fastest and best that I have found to date. I have tried and regretted other methods, eg the BIN. I might try the Zinsser 123 soon.

 

[joe-90]

If you sand it with 120g you will have no primer or undercoat left!?!?!

And the 2010 voc undercoat takes day to harden.

Are you really that clueless? What do you really do for a living?

 

[opps]

Are you really that clueless? What do you really do for a living?

Do me a favour Joe. On monday prime some mdf, on tuesday undercoat it, on wednesday try to sand it with 120 and tell me what happens.

 

[joe-90]

You get a perfect finish. You really have got to understand your medium.

 

[opps]

You get a perfect finish.

I have never obtained perfection, nor will I ever.

I will however continue to strive towards it.

 

[joe-90]

Well you could start by ditching all your power sanders and additives.

 

[opps]

i started off years ago with no sanders and no additives.

Why would I want to take a backward step?

Why would i want surfaces with sandpaper scratches, clouds of dust and inferior finishes.

Surely the point of learning your trade is to improve the finish that you can provide your customer.

After all they are the people that pay me.

 

[joe-90]

Well you'd better tell that to the rest of the trade and the paint manufacturers then hadn't you?

 

[opps]

Sorry joe

I really don't understand the hostility regarding the use of sanders. They are industry wide.

I am not aware of any industry move to ditch them and move back to hand sanding.

Are you privy to something that I am not?

Please do tell if you are.