Thread: MDF Primer for 2 pack paint

I've sprayed a fair amount of MDF in 2 pack paint and have had good results to date. I'm no expert but I think the key to success is to use the recommended primer that the top coat manufacturer recommends. I use a 2 pack high build primer made for the 2 pack top coat and it fills the MDF well enough that several coats then sanding is enough to prep ready for the top coat. I give the cut/routed edges an extra few coats of high build to fill the grain. Matching the primer to the top coat is critical as it's a chemical bond taking place and any old primer won't do.

If I remember without going down to shed, the brand of paint I use mostly is Protec. Not cheap but leaves a mirror finish. Can also be sanded and buffed if needed. There are lots of brands that have chemical compatibility with each other but I'd consult a paint supply place to make sure first.

A few tips I've leant with 2 pack is to use light coats and let it flash off for 15 minutes before applying the next coat. If you don't let the solvents flash off they will be trapped by the next coat and cause problems. If you get some dust or insects landing in your fresh paint just use a pair of tweezers to remove the offender then hit it with another coat while still wet and it will flow out and fill. Alternatively you can wait till it's dry then sand them out but that will most likely need another top coat. It's also important to let the paint stand after mixing for the recommended time before using to allow the chemical reaction to start before spraying. Make sure you have good ventilation and wear a suitable mask as this stuff is really toxic.

It took me a fair amount of trial and error to get my system working right. Experiment a bit on some scrap first with different gun pressure and various thinning volumes till you're happy with the result.

Thanks for the reply and extra info Maggs, much appreciated.
Do you use Automotive 2 pack - or a different type?
Thanks
Geoff

Originally Posted by garfield

Thanks for the reply and extra info Maggs, much appreciated.
Do you use Automotive 2 pack - or a different type?
Thanks
Geoff

I use automotive grade and it's fine for MDF work. Probably a bit of overkill but I'm a bit a of perfectionist. The primer is the most important. If you use a standard primer as opposed to a high build it will take a few sessions to fill up all the little pin holes and imperfections that MDF has and it won't fill the cut/routed areas so well. I buy the Protec paint and primer from my local automotive paint shop. There are lots of brands/types of 2 pack to choose from and the prices vary greatly. Like anything you usually get what you pay for.

I've seen some people using spray putty under the primer on cut edges but I'm not a fan of it. The edges are the most likely to get banged up and spray putty is a bit soft so it might allow the top coat to crack if dinged. Maybe I'm paranoid but the 2 pack primer is as hard as nails when cured and provides a more durable finish IMO.

The last kitchen I sprayed was white and done over 2 years ago and today it still looks like the day I did it. I just sprayed a motorcycle with the same Protec paint and it turned out really nice done in gloss black which is the hardest colour to get a good finish as it magnifies every imperfection. A friends wants me to spray his new kitchen gloss black and I'm trying to talk him out of it as I know it will take a lot of prep to get a nice finish

Note that 2 pac paints need an air-fed respirator for safe spraying (unless they are iso-free), so at the very least buy new organic vapour filters for your face mask and throw them out at the end of every day (unlike the usual paint solvents - where it's 'sniff-sniff, I should put new filters on' - you can't smell isocyanates until the concentration is well over the safe exposure limit, by which time you have already been breathing it in for an unknown amount of time)

Originally Posted by maggs

I use automotive grade and it's fine for MDF work. Probably a bit of overkill but I'm a bit a of perfectionist. The primer is the most important. If you use a standard primer as opposed to a high build it will take a few sessions to fill up all the little pin holes and imperfections that MDF has and it won't fill the cut/routed areas so well. I buy the Protec paint and primer from my local automotive paint shop. There are lots of brands/types of 2 pack to choose from and the prices vary greatly. Like anything you usually get what you pay for.

I've seen some people using spray putty under the primer on cut edges but I'm not a fan of it. The edges are the most likely to get banged up and spray putty is a bit soft so it might allow the top coat to crack if dinged. Maybe I'm paranoid but the 2 pack primer is as hard as nails when cured and provides a more durable finish IMO.

The last kitchen I sprayed was white and done over 2 years ago and today it still looks like the day I did it. I just sprayed a motorcycle with the same Protec paint and it turned out really nice done in gloss black which is the hardest colour to get a good finish as it magnifies every imperfection. A friends wants me to spray his new kitchen gloss black and I'm trying to talk him out of it as I know it will take a lot of prep to get a nice finish

I went to kgp automotive paints this afternoon and the guy there has lined me up some polyfiller primer (I think that's what it was called) from one of his friends who sprays kitchens at his business, apparently it's a primer specially designed for MDF which takes 2 pack automotive paint on top of it.

The wife would like a high gloss white so phewwww she doesn't want black!

Do you have a DIY booth Maggs?

I'd love to see some pics of your work mate
Cheers again,
Geoff

Originally Posted by Master Splinter

Note that 2 pac paints need an air-fed respirator for safe spraying (unless they are iso-free), so at the very least buy new organic vapour filters for your face mask and throw them out at the end of every day (unlike the usual paint solvents - where it's 'sniff-sniff, I should put new filters on' - you can't smell isocyanates until the concentration is well over the safe exposure limit, by which time you have already been breathing it in for an unknown amount of time)

Thanks master splinter, I've been recommended a half face painting mask and filters today from the guys at kgp this arvo when I was there... certainly sounds like nast stuff that isocyanates!

Thanks
Geoff

When I painted the kitchen I just did it in my shed and closed the roller doors and cracked a few windows. It got really misty so I ended up opening up the roller doors as I couldn't see what I was doing. I had the doors hanging on a wire strung up across the inside of the shed. Only got a couple of bugs but removed with tweezers and touched that up wet and it was fine.

Next job was a motorcycle and this time I had one of those temporary carports from Supercheap and I enclosed the sides with plastic so it was well sealed. The floor was dirt/grass and covered in plastic too. I had a small opening down near the floor on 2 side to try and create a natural air flow to try and remove the overspray. Didn't work at all and I got more bugs and crap in the paint than in the shed. I spent a lot of time removing little bugs with tweezers and touching up. For some reason bugs are really attracted to this paint. Before I started I sprayed a whole large can of insect killer and waited 30 minutes for the effect to kill them. Failure.

Next job was to paint a pair of motorcycle forks. I couldn't be bothered to setup anything so I just did it outside in the open with a very light breeze. The only prep was a light watering down on the ground prior to starting. The result was no bugs or dust and a perfect finish. Go figure.

If you setup a temp booth I think it's mandatory to have some sort of exhaust fan and filter setup. I didn't have anything on hand except my dust extractor and I didn't really want to fill that with overspray so I canned that idea. If I was doing a lot of spraying I think I'd need to setup better. The biggest problem in a non vented booth is you can't see what you're doing and you end up missing spots on the job. A pair of disposable full coveralls is a good idea too as this stuff is really sticky for a long time after it's sprayed and of course it's toxic too if you get it on your skin. The first time I ever used 2 pack I was wearing a pair of sandals and I had black toenails for a few months until it grew out.

I don't have any photos of the kitchen but i do have a few of the bike.

Before:


After:

I really like your finish on the bikes Maggs, especially the black one! Did you have any spraying experience prior to doing your kitchen or your bikes?
I have a few old exuaghst fans kicking around at home and was considering making some filters etc and grab a few fans to create a "spray booth" under my colourbond pergola.... I may look at one of them supercheap auto set ups too though with the same concept in mind.

Do you use an expensive gun and compressor Maggs? I have a 1.4mm needle hvlp gun which I haven't used as yet, I'm hoping it will do the job it's a $40-$50 from ebay. I might invest in another for this project though as I've been informed that a 1.8mm needle is the way to go for the primer.
Thanks once again mate
Geoff

Just remember that individual sensitivity to isocyanate varies wildy; some people can use it for years with no apparent ill effect, some will develop an occupational asthma and decrease in lung function after number of year, some will feel sick as a dog several hours after using it, and the odd person can drop dead from a severe reaction.

Research on use of half-face respirators for isocyanates:
Respiratory protection from isocyanate e... [J Occup Environ Hyg. 2006] - PubMed - NCBI

(edit)....see also:
S/P2 Newsletter
2K Safety - Leason learnt - MIG Welding Forum


Coveralls, a head sock, gloves and goggles and maybe even some barrier cream are also sound investments.

If you are after a simple colour like white, Hi-Chem makes an iso-free 2k.

The black bike is the red bike after I painted it.

I don't consider myself as an expert spray painter but I'm competent and have done quite a bit of it over the years. I learnt by watching a few pros and picked up the important points like keep your wrist joint as still as possible and to maintain a constant sweeping motion and a consistent distance from the job. My first gravity fed gun was a cheaper unit around $100 with a 1.8 mm nozzle. It was ok for spraying lacquer and primer. When I decided to paint a 21' Bertram boat I invested in a quality Italian made gun with a 1.5 mm nozzle. That cost around $500 about 10 years ago. You don't need an expensive gun to do a good job but it does help. A great gun with poor technique won't produce a good result but a cheap gun in the right hands can produce an acceptable job. Guns are cheaper now than when I bought mine so I think you'll pick up a nice gun for sub $300. Star guns seem to be a popular entry level gun these days. I saw one last time I was in the auto paint store and I think it was around $200.

Setting up an exhaust fan and filter will make the job a much more pleasant experience for sure. If this is your first major spraying job, do some practise spraying on some scrap or less important items before you plunge in to the kitchen. The kitchen isn't particularly difficult a job as it is mostly flat surfaces. It gets harder on curved and complex surfaces so I'm sure you will be ok if you take your time don't try and apply too much paint in one go. The first coat should only just cover the primer barely. Next coat after 15 minutes or so can be a bit heavier then finally hit it with a good dose of paint but not too much as you will get runs. I generally run my gravity fed gun at around 40 PSI when spraying 2 pack but you'll need to experiment a bit either side and see what works for you.

Also bear in mind that if you don't get an acceptable finish off the gun you can sand it with 800 grit then 1200 then 2000 and buff it. To get a good finish off the gun takes a bit of experience and some good luck. Even the pros can't do it all the time.

There's few things I find more satisfying than sitting down with a beer admiring your paint work after it's finished and saying "I did that".

Originally Posted by Master Splinter

Just remember that individual sensitivity to isocyanate varies wildy; some people can use it for years with no apparent ill effect, some will develop an occupational asthma and decrease in lung function after number of year, some will feel sick as a dog several hours after using it, and the odd person can drop dead from a severe reaction.

Research on use of half-face respirators for isocyanates:
Respiratory protection from isocyanate e... [J Occup Environ Hyg. 2006] - PubMed - NCBI

(edit)....see also:
S/P2 Newsletter
2K Safety - Leason learnt - MIG Welding Forum


Coveralls, a head sock, gloves and goggles and maybe even some barrier cream are also sound investments.

If you are after a simple colour like white, Hi-Chem makes an iso-free 2k.

Hi Master splinter,
Thanks very much for that information. I had no idea that there was that much danger involved in spraying 2 pack paint.
I knew there were precautions that needed to be taken as it's not good for you but reading those links you supplied makes me wonder if I even want to finish the kitchen in 2 pack now

Is there an alternative to 2 pack with similar results?

Originally Posted by garfield

Is there an alternative to 2 pack with similar results?

We wanted a matt finish to our doors and ended up using a water based trim paint from Haymes.

Takes longer to "cure" and won't get as hard as 2 pac, but we got exactly the finish we wanted and are very happy with the results.

Originally Posted by Master Splinter

Just remember that individual sensitivity to isocyanate varies wildy; some people can use it for years with no apparent ill effect, some will develop an occupational asthma and decrease in lung function after number of year, some will feel sick as a dog several hours after using it, and the odd person can drop dead from a severe reaction.

Research on use of half-face respirators for isocyanates:
Respiratory protection from isocyanate e... [J Occup Environ Hyg. 2006] - PubMed - NCBI

(edit)....see also:
S/P2 Newsletter
2K Safety - Leason learnt - MIG Welding Forum


Coveralls, a head sock, gloves and goggles and maybe even some barrier cream are also sound investments.

If you are after a simple colour like white, Hi-Chem makes an iso-free 2k.

Originally Posted by maggs

The black bike is the red bike after I painted it.

I don't consider myself as an expert spray painter but I'm competent and have done quite a bit of it over the years. I learnt by watching a few pros and picked up the important points like keep your wrist joint as still as possible and to maintain a constant sweeping motion and a consistent distance from the job. My first gravity fed gun was a cheaper unit around $100 with a 1.8 mm nozzle. It was ok for spraying lacquer and primer. When I decided to paint a 21' Bertram boat I invested in a quality Italian made gun with a 1.5 mm nozzle. That cost around $500 about 10 years ago. You don't need an expensive gun to do a good job but it does help. A great gun with poor technique won't produce a good result but a cheap gun in the right hands can produce an acceptable job. Guns are cheaper now than when I bought mine so I think you'll pick up a nice gun for sub $300. Star guns seem to be a popular entry level gun these days. I saw one last time I was in the auto paint store and I think it was around $200.

Setting up an exhaust fan and filter will make the job a much more pleasant experience for sure. If this is your first major spraying job, do some practise spraying on some scrap or less important items before you plunge in to the kitchen. The kitchen isn't particularly difficult a job as it is mostly flat surfaces. It gets harder on curved and complex surfaces so I'm sure you will be ok if you take your time don't try and apply too much paint in one go. The first coat should only just cover the primer barely. Next coat after 15 minutes or so can be a bit heavier then finally hit it with a good dose of paint but not too much as you will get runs. I generally run my gravity fed gun at around 40 PSI when spraying 2 pack but you'll need to experiment a bit either side and see what works for you.

Also bear in mind that if you don't get an acceptable finish off the gun you can sand it with 800 grit then 1200 then 2000 and buff it. To get a good finish off the gun takes a bit of experience and some good luck. Even the pros can't do it all the time.

There's few things I find more satisfying than sitting down with a beer admiring your paint work after it's finished and saying "I did that".

Thanks for that info maggs.

I hope to pick up another half decent gun for around the $100 mark, which I hope will come with few different neelde sizes.

master splinter has me really questioning using 2 pack after reading the links he gave me... what type of mask protective set up do you have maggs?

Sorry for all of the questions - but promise to stop soon

I can't remember what brand the mask is and I'm not at home right now. It's a replaceable cartridge type with different cartridges for different applications. If you take the precautions you'll be ok but it is not something I'd be happy doing for a living. I guess that's why the industry is moving to water based paint systems.

Forgot to mention my compressor last post. Mine is a twin cylinder 15 cubic foot per minute with a decent size reservoir tank. You can get away with a smaller capacity but you just have to wait for it to catch up a bit more often.

Originally Posted by maggs

I can't remember what brand the mask is and I'm not at home right now. It's a replaceable cartridge type with different cartridges for different applications. If you take the precautions you'll be ok but it is not something I'd be happy doing for a living. I guess that's why the industry is moving to water based paint systems.

Forgot to mention my compressor last post. Mine is a twin cylinder 15 cubic foot per minute with a decent size reservoir tank. You can get away with a smaller capacity but you just have to wait for it to catch up a bit more often.

Thanks Maggs.

I think I'll need help chosing a decent mask now. I'm still a little worried now with 2 pack.... If there wasn't so much work involved in acrylic I'd have a crack with that, but I'm not too sure it's any good for MDF anyway.