Rattle Can — Primer and Paint advice (fast job)

[multimarcus]

Hello there,
I hope you can help with the issue I am having.

Need to spray paint a piece of fibreglass coated with bondo, with automotive cans from Halfords.
After a few attempts with black gloss Halfords, I have sanded the whole piece down and applied grey primer again as of last night, in order to start again with Halfords Black satin, which should be easier and more forgiving.
I am now considering applying a second layer of primer before painting with Black Satin.
Is there any way I can speed up the flash time in between the two coats of primer?
ie heaters, fans etc

Alternatively I could choose to go with simply one layer of primer and then spray the Black Satin on top.
When it comes to the Black paint, I usually apply one light layer of paint and after 20 mins a deep one.
At this point how long should I wait until I can spray another layer of Black Satin?

Many thanks for your help
Best wishes

Marcus

 

[cumbriasteve]

Difficult to give an accurate time as such:

The temperature is the governing factor, I used rattle cans a lot on small bike parts when I was into restoration and always liked to warm the part up a little, I used a hair dryer or hot air gun, not too hot though or the paint dries too fast and affects the final finish.

I also made sure the area around the task was warm, this meant I could apply 3 or 4 top coats in very little time, rarely taking more than 10 mins in total.

Ideally you should recoat before the first coat dries off too much, so it bonds into and not sit on top.

Of course if you apply the second coat too early it all becomes too wet and heavy and lovely runs appear.

Great fun painting isn't it?

 

[multimarcus]

Thanks Steve for the quick reply!
Keeping the place warm is definitively a good idea.
And warming up the part very good as well.
About the topcoat layers, do you start with a light one and then go deeper (more detailed) with the others?
10 mins in total for all of them? wow, so that must have been where I was doing it wrong.
And that explains why the paint looked different in some of the areas.
About the primer, does it make sense to keep the part warm in order to speed up the drying time?
I don't care too much if the paint cracks in a month or so, as long as it lasts for couple of weeks
Thanks for your help! I'm a bit of a newbie.
MM

 

[cumbriasteve]

Never had any cracking;

Yes warmed it prior to the primer also

By warm I mean just warm, I never really gave any thought to difference in layers, tended to spray them all about the same, not too heavy but enough to give a clear covering.

The difference in appearance may be cold areas that have bloomed slightly or dried back at a different rate.

 

[multimarcus]

Great! One last question about the primer, is 24h a real minimum or can I wait a little less?
I am trying to cut corners here, but I basically need to deliver this piece as of tomorrow
Thanks!
MM

 

[cumbriasteve]

There is a small risk that touch dry primer could react with a top coat if done too early.

This is what I would do...do the same at your own risk:

Spray the primer onto the warmed item and then use a hair dryer to dry the primer and get it quite warm, leave it for an hour, perhaps warming again at the half hour point.

If it appears totally dry then go for it and keep fingers crossed.

 

[multimarcus]

Thanks!
I will send an update soon!
Have a very nice weekend

MM

 

[multimarcus]

Update: I did it, sprayed three layers of Primer, first heavy, (left it overnight) second and third light and left the piece in the beautiful sunshine for two and half hours.
Then sprayed black satin.
Now I have one side with a bit of flashing (was spraying in dimmed light), so I might have to wet sand it and redo it.
And sprayed some blotches on the other side (argh, never happened before); I am now wet sanding it lightly and repaint it...
Fingers crossed, it was pretty much there.