Painting over synthetic paint

[sixdogsisback]

Can anyone tell me if there is a primer/surfacer which is suitable for painting over synthetic paints and will not cause it to blister.

I repaired some torn bolt holes on the rear wing which had torn when I had a wheel come off. The welder burned small areas of paint. When I tried to touch prime the bare areas with some old cellulose primer, intending later on to respray the whole wing, it blistered the old paint, which must be synthetic type, as it turns out. I did not want to strip the old paint down to bare metal. Any advice welcome.

Thanks, Clive.

[Alec]

Hello Clive,

Cellulose tends to do that unless the paint you are covering is cellulose as well.
You would need to put a coat of bar coat on first which should prevent that happening.

Alec

[sixdogsisback]

Hello Alec,

I've not come accross bar coat. It's a good few years since I did any paint jobs on cars. Would the bar coat act as a primer /leveler, or would I need to apply a further coat before the finishing paint? I'm not bothered about perfection, but I like the car to look tidy.

Clive

[Alec]

Hello Clive,

I've never used it myself but it is designed to allow the use of an incompatible paint by sealing the lower surface. You would need to enquire with a local paint stockist I would think.

Alec

[rayofleamington]

I've used a bar coat on a respray, however you'll need to cover the whole wing to do this touch up.
I've had synthetic coach paint mixed up in the past, but for a small quantity it won't be ideal. I used quite a bit and hand painted the inside of boot and inner wings etc... Decent coach paint will have a good self leveller, and can be used for discreet repairs on the body.

If you're keeping the car a long time it may be worth getting some (and making sure the container is airtight!!) but otherwise you could try and touch up with synthetic paint - if it works then you'd need a paint factor to make up some cans for you.

[sixdogsisback]

Hello Ray,

I've used coach paint in the past. too many years ago to count now. It gave good results. The paint factors are getting like hens teeth around here. I see Jawel paints are still around and there's a branch in Bromsgrove, near where I live. I think I will see what they have to do the job. I got to be quite good at spraying cellulose in the 60's and have used synthetic paints in the 80's, but with so many advances in technology, I feel a bit lost now. When you buy an old car, like mine, it's hard to tell just what paint has been used on it over the years.

thanks for input.

Clive.

[dustyfog]

Hi clive. you can get an isolator for sealing cellulose paint, its called u-pol bar coat the only thing its only avaliable in 1ltr cans for use with a spray gun. the bar coat is a r.f.u paint ( ready for use ) a good couple of coats normaly does the trick, but you may need to use a fine wet n dry sand paper inbetween coats in hot weather as it dries very quick as said earlier you must repaint all the area/panel with the bar coat if using cellulose as a primer and top coat. hope this helps. dusty.

[sixdogsisback]

I have now sprayed the wing with synthetic paint. The primer I bought from Jawel Paints went on very well with no reactions and hardly needed any sanding.

Unfortunately, I have got one or two runs in the finish coat and need to deal with these. There appears to be some confusion as to whether I can sand the finish and then get the shine back with cutting compound, also how long I should leave the paint to harden. I tried some 1200 grit wet and dry on a small test piece I sprayed, followed by some rubbing compound which I bought from Halfords. I failed to restore the shine on this, but the paint still seemed quite soft. the compound seemed too coarse also

Any suggestions?

Thanks, Clive.

[linearaudio]

I have now sprayed the wing with synthetic paint. The primer I bought from Jawel Paints went on very well with no reactions and hardly needed any sanding.

Unfortunately, I have got one or two runs in the finish coat and need to deal with these. There appears to be some confusion as to whether I can sand the finish and then get the shine back with cutting compound, also how long I should leave the paint to harden. I tried some 1200 grit wet and dry on a small test piece I sprayed, followed by some rubbing compound which I bought from Halfords. I failed to restore the shine on this, but the paint still seemed quite soft. the compound seemed too coarse also

Any suggestions?

Have a look at the article in "useful tips" about spraying synth. Should clear up a few questions. Basically get it right first time or start again

Thanks, Clive.

[sixdogsisback]

Where can I find the article " usefull tips" about spraying synth?

Clive

[PSL184]

http://www.mmoc.org.uk/index.php?name=P ... ic&t=22760

[sixdogsisback]

Thanks for article. But It still does not answer the question of whether the finish can be cut back and then repolished, like you can with cellulose, and how long you should leave it before attempting this. The paint still seems very soft.

Thanks, Clive.

[dustyfog]

HI clive, you can,t cut back synthetic paint like cellulose as synthetic is more oill based than cellulose so looses its shine. look at my thread on spraying synthetic.

[dustyfog]

Hi clive, give this a go mate

Paint runs and sags
If you are unfortunate to get a run or sag in one or more of the panels don’t panic. If you have spotted this before the paint is dry you can was off the affected area with thinners , do not use cellulose thinners as this will fetch off the primer as well, use the primer thinner or panel wipe , all your aiming to do is to wash off the top coat . Let’s say you had a run on a wing you need to wash off the entire wing being careful not to splash any thinner on any other areas. Leave it over night to dry nib wing with 800 wet and dry mask off whole car tack off wing and respray

Dry runs
Think of synthetic paint as an egg custard, when it’s first sprayed, sort of hard on the outside but runny underneath. Synthetic paint is very much like this as it takes a lot longer to dry so making re-working much more time consuming, you cannot rush re-working synthetic
You can scrape off the run with a flat blade scraper going past the run into sound paint, this will leave a deep groove where the run was, feel with you finger to see if its still tacky, if it is you will have to leave this over night to cure, you could try wet flatting with 400 wet and dry using wet and with soap, but this only just seems to make the paint roll and then you end up with more scratches .so best leave over night to cure after you have scraped off the run, then do as above.

this is from my thread i wrote on spraying synthetic which is linked above

hope this helps
dusty

[sixdogsisback]

Thanks Dusty,

It does not look too bad now I've put the lights and bumber back and cleaned the rest of the car up. It's still better than the rest of the car. I think I will leave the paint to really harden, then flat it down and respray it.

Clive.

[dustyfog]

hi clive. if you wanted to leave it, i would leave it at least a month before trying any re-work, then i would rub it all down the day before painting just to make sure the affected area with runs has cured. if you need any more advice just give me a shout and i will try and help you out.good luck with it

dusty

[sixdogsisback]

Hello Dusty,

Yes, good advice. I think I probably put too much paint on. The runs will be thicker anyway and I had thought they might take a long time to harden right through. On your spraying tips article, you mentioned polish and in particular Silicon. What is the best way to remove this prior to preparing bodywork for spraying? The polish I had put on my car is so good, the masking tape would not stick to it and anything I place on the roof, just slips straight off again. You would not want to put paint on that.

Regards, Clive.

[dustyfog]

Hello clive,

the best eay to remove wax on a panel is to wash off the panel with panel wipe, avaliable form all good motor factors for about £10.00. Use cotton rags (clean old t-shirts) but no material that is shiny as this dosn't hold the thinners very well and it also dosn't pick up dirt etc. if you were going to leave the panel for a while you could use synthetic thinner but only when its cured after a month, this is stronger and will cut through the layer of wax quicker. When doing the washing off please use rubber gloves as it can irritate skin. Also when washing off the panel change the cloths after each wipe, this is to make sure you remove the wax and not just spread it over the panel. If you need any additional help give me a shout.

hope this helps

regards dusty

[sixdogsisback]

Thanks for all Dusty, I will get some.

Clive.

[dustyfog]

not a problem clive your welcome