Dust on the final coat of enamel

[HTM]

Hi all

I just wanted to know what i can do with small amounts of dust on a final coat of enamel high gloss that i have painted on MDF doors. I have painted two coats of under coat and three coats of the enamel finish. They have been sprayed with a hvlp spray gun and i just wanted to know if there is a way to maybe sand and buff and if so with what product. I have used an 800 grit paper with an orbit and then use turtle wax on it but can still see the scratches where i have sanded.

This is my first attempt at spraying so i am not too experienced with the dos and donts of spray painting or finishing. ANy help much appreciated.

[joez]

Hi HTM, Yes it can be done, flats surfaces are pretty straight forward but corners are tricky.

Make sure your paint is really dry, you should be getting a fine dust. If your sandpaper is clogging or your getting little balls of paint let it dry a little longer.

800 grit is still pretty course, you'd need to go higher grit and try finishing with an auto cut/polish to bring back the shine.

If i were doing it i'd sand 800/1200/2000 and cut and polish. With the 800 grit you'd probably only need to sand for a short time just to level out the surface.

If you've done it right the panel will come out like glass, which can cause problems becuase the other panels wont look as smooth.
joez

[Christos]

Spraying a piece is not something that I have done but using a brush etc I have. As to dust getting onto the piece that I was finishing, this can be a real problem in my little garage.

I was doing the final coat outside the garage and getting a better finish then moving the item back in the garage. There could be a lot more people giving far better advise on what to be aware of when doing a final finish coat. Especially when it comes to spraying.

[cuoey]

As Joez stated cut back with 2000 wet and dry, then use buffing compound once the surface is flat.
I use Farecla G3 followed by G10 for Polyurethane or lacquer sprayed doors. G3 may be enough though.

[HTM]

Thanks for that guys. I didnt know the paper went up that high. I'll have to get some and try it out. Thanks for all the advice. It was probably a stupid thing to do but the only store that was open today at 5.30pm was Bunnings and i ask someone in their paint section the same question and they told me the only thing i could do was sand back and re-paint.

[HTM]

Would i get the buffing compound from any paint store?

[joez]

You should be able to get a buffing compound (car cut and polish works) and the higher grit sanderpaper from an auto paint suppliers, or even supercheap autos.


joez

[durwood]

Air dry enamel isn't meant to be cut back and buffed it is designed to eliminate these steps which saves labour costs making it a cheaper method of painting.

The enamel is formulated to dry at a maximum level of gloss. if it is sprayed properly it will always be glossier than if you attempt to buff it. Just touching it even with a soft cloth or lambwool buff leaves tiny swerl marks in the finish. If it is only a small amount of durt don't rub or buff try washing it with adamp chamous it will usualy pull the dust out of the surface.

You won't find any instructions for the cutting and buffing of air dry enamel. do so always results in a poorer gloss than is possible.

Enamel drys by reacting with oxygen in the air thats why you get a skin on the top of the paint in a tin. You must let it dry for several days. or you may make marks in it when it is still soft. If you have time let it dry for a long time week is good month is better the harder it is the more you can rub and buff it you intend to

If you are in a hurry, rub it smooth eliminate all sources of dust and respray it that is a lot quicker and easier (and cheaper) than buying paper and compound to try and fix it and it still might not be good enough. If you find it has dirt in the surface which is unacceptable while it is wet wash it off before it dries using turps and rags. Bit messy (use gloves) use one soaked rag to dissolve the paint, a second to wipe the wet residue away. when the rag gets too messy throw the rags away and use new clean ones in a few minutes you will be back to where you were before you started sprayng and you can then do it again without the disaster you got first time . This is especially so when you get runs etc. It will take days to dry enough for you to rub it flat where washing it off leaves it new in minutes.


Having said that if you do have dirt in the surface doing what is suggested using very fine paper and then an auto buffing compound you should be able to alter the gloss and remove some of the dirt so the surface improves.

As mentioned the enamel is slow drying so it has lots of time to pick up dust floating in the air as it stays sticky for so long. You need to prepare to prevent any contamination getting into the enamel while you spray and while it dries.

A proper dust free is booth is a start but not probably possibe for you.

Even with a proper booth you still can get a poor result. so try and eliminate any possible cause of dirt.

*Outside in clean air is a good start.

*In the morning before the wind picks up

*Water the area around you down to lay dust

*strain the paint

*blow off the surface with compressed air immediately before you spray

Then tack rag the surface

*wipe the air hose about 2 meters back from the gun before you spray especially if you have taken the hose off the gun and dropped it on the floor before hand. You will sprinkle dust over a job laying flat from the hose as you spray if you don't

*Make sure you don't have dust on your clothes especially if you have been dry sanding the timber or anything else in them previously

*Spray the job and take it to a room or area immediately where it would be difficult for dust to settle on it once its finished as it will get dust in it for at least 1/2 hour after the paint is applied. Especially if you are spraying more things after it.

* A good way to help stop the dust is to set up a plastic sheet so you can put your job underneath once done. a tent type arrangement is even better you have a dust free area where its hard for dust in the air to settle onto the surface.

As these are doors you may also be able to work out a system where you can paint the surface and then turn them upside down ( say 2 nails in opposite edges) you then put the doors resting on the nails on two bits of timber ) its a bit hard for dust to settle on the paint when its underneath the door.

[HTM]

Thanks Durwood for all the info. I tried to sand back and buff today with not very good results. The doors came out smooth but the gloss wasnt there in the spots where i sanded.

I think i will try water based gloss by Resene to see what results i get, but will also take into consideration all the other points. I did sand in the clothes i painted in and should have wet down the floor. So might see if there is a better result taking that into consideration.

I paint in a room that is about 4mtrs x 3mtrs and have a shelving system in there where i stack the doors. I guess whilst i am spraying there is the air from the gun blowing small amounts of dust around the room, even though i am using a HVLP system. I would like to try having the doors hang upside down but would need to work out how to do that. If i used the nail system would that not leave some mark on the surface of the door?

Anyway thanks for everyones help and hopefully will work out a system and will post results.

[durwood]

you would use fine pqanel pins or nails , one each end of the top and bottom of the door edge.

The holes left on the bottom would not be seen unless on wall cupboards, so just a speck of filler and a dab of paint after would fix them opposite for doors close to the ground. If you use long supports you can spray the front and roll it over on two nails on one end and have it upside down.

[Lumber Bunker]

EEE will work no?

[Johncs]

I would like to try having the doors hang upside down but would need to work out how to do that. If i used the nail system would that not leave some mark on the surface of the door?
.

Presumably, you intend to install hinges and some kind oif closing mechanism. The places those will be installed are good places for nails, or even screws, to hold it while you paint it.

[Johncs]

EEE will work no?

I was thinking of the Tripoli powder, but other cutting/buffing compounds already mentioned should do as well.