Dry (matt) patches in paint

[Kernite]

Nice to be back after a long absence. Still trying to develop my skills and realising more and more that its hard as an amateur to achieve perfection or get close to professionals.

Just done my first bit of serious welding - bottom panel and sill of T25 - not sure I ever thanked Weldequip for my Portamig . However moving from practice beads to thin panels which flex with heat was a bit of a learning curve.

Anyway back on topic - my painting has failed quality control - I have some matt (dry) bits. Spraying Cellulose using an Anest Iwata W400 WB Gravity Spray Gun. Thinned about 20%.
Running about 40psi.

I'm not getting an enormous spray pattern (looking at some youtube videos the spray width is quite large) mine is just an inch or two. Is the "dry problem" problem caused by too little paint, should I thin it a bit more, or up the pressure, or open the adjuster to feed in more paint. Had a similar issue with my Landy but was using enamel.

How long should I wait for each pass - a few minutes or 15mins? The weather was warm so flashing off fairly quick.

In that I have to redo how quickly can I sand back (800 grit?) and repaint or will I be able to bring up a gloss finish just by sanding and polishing what I have already put down?

Whats a good number of coats and do I finish with lacquer?

sorry lots of questions - will re read how to paint on this forum.

I would like to repaint tomorrow as to re mask takes time.

Many thanks for any advice.

 

[norsa]

Your mix should be 1:1 if its cellulose. Check the data sheet, maybe do the drip test then get your gun set up properly on a piece of old steel. Cellulose is pretty unstable stuff so don't expect a perfect finish. You may be able to wet flat back but if it clogs your paper............not dry enough, hard work.
Nick

 

[ajlelectronics]

20% is nowhere near enough. I would start with 50/50 then move to 25/75 for the final coats.

 

[carbon]

Just had a quick look at the instruction manual for the spray gun, recommended air pressure is between 26 and 28.5 psi depending on the air cap that's fitted. Which means air consumption could be between 8.1 and 13.7 cfm. What air cap do you have and what size compressor.

But as the others have suggested try more thinners first.

 

[pedrobedro]

50/50 for cellulose and no need to over thin to finish coat, you'll just end up with runs. Use a good quality nitro thinner not standard or gunwash, you can get different timings fast medium or slow to suit your style and give you a good shine without much cutting and polishing after. I know it costs a lot more but it's worth buying a litre for a job you want to look presentable. If you can't get a good finish with a W400 I'm afraid I will have to confiscate it

 

[Kernite]

Thanks guys for quick and helpful (as always) responses - I clearly made a lot of wrong assumptions, so have spent the morning doing more researching and watching videos (clearly should have done it before). Found out cellulose should only be sold for vintage cars and I am not sure mine is vintage yet! So not sure I should even be using it.

I will speak to the supplier (bgr bank holiday) but will assume 50:50 as no documentation with paint to indicate and I should have asked. Previous paint supplier for the Landy wrote the dilutions on the tins. I'll also use the stick test to check existing consistency.

The gun is an old one (on long term load from a body shop guy - I probably should return it or offer to pay for it as 5 years is pushing it) so probably different from the WB model ( I was lazy and cut and pasted to get spelling right) - using Carbon's route I pulled the manual and it says 29 to 43 psi so probably was not far off for the viscosity I was using but will lower pressure for the thinner paint. Just editing as I forgot end cap - is this the needle it says V2 on the end cap and I 1.4 inside on the fluid nozzle. And yes pedrobedro the one thing I cannot blame is the gun. The same goes for welding - its the guy holding the gun thats the problem here.

Not sure of the capacity of my compressor but its old and thumps, has a big tank and has not struggled with anything yet - and challenges my 13 amp plug.

I think I tend to panic when I have loaded the gun and probably should spend more time practicing and setting up correctly - something that is probably automatic if painting on a regular basis. I never know how long the paint can stay in the gun - is there a trick to dip the nozzle in thinners between coats. So it all becomes a desperate rush.

Will now see if the paint can be flatted back and will respray when the wind drops (yes I am outside as high top does not quite fit in the garage and there's no room anyway).

On with the journey ...

 

[pedrobedro]

2 bar, about 30 psi should be about right, don't go too low or the paint will not atomise and the fan will only be small and you'll be back where you started. As long as you are not claiming to be using the paint for professional purposes you are fine using cellulose so don't worry about it. There's no need to dip the nozzle in anything and don't panic, the paint will not set in the pot unless you leave it for a couple of weeks