Paint Spraying

[Chris KC]

I'm contemplating spraying my Box Saloon at home (with cellulose).

Perhaps the first thing I'll need to do is acquire a suitable compressor. My local paint merchant advises 3hp/ 100L as a minimum - n.b. but hasn't seen the size of the car.

Any DIY paint sprayers out there? Is 3hp/ 50L big enough to tackle an A7? Any preferred brands, or pitfalls to watch out for?

I have found several good "how to" articles about the painting process, but at this stage would welcome any input on suitable basic equipment and any experience specific to A7's...

Thanks in advance.

[Ivor Hawkins]

When it comes to spraying and compressors, bigger is definitely better!

With the 100 litre receiver you are less likely to run out of air and ruin the finish as the gun struggles to atomise.

[Howard Wright]

Hi Chris

I’ve sprayed three A7s using a 50ltr compressor.  I got lots of good advice from a paint supplier (Border Automotive in Shrewsbury) but I guess there will be suppliers nearer you.

I think the best possible advice is ‘preparation’.  Every hour you put in to preparing the job will reap rewards.  I split the job up into as many small parts as possible; wings, bonnet, doors and found using a small gun was better than a big one.  Lots of thin coats rather than one thick coat and be prepared to flat back and start again.

Also remember a good mask and that the overspray will go everywhere.  If possible deck out your spray area with plastic dust sheets.  Oh and don’t try to spray when the temperature is less than 10 degrees and preferably when it’s more than 15!

Good luck!

Cheers

Howard

[andrew34ruby]

Chris, I've been DIY spraying for over fifty years. Yes 3hp should be ok. 50 litres might be ok depending on the spray gun and how you work. If you tried to spray all of a 7 saloon quickly, without any pauses, then you probably would run out of air. But if you spray a door fairly casually, then a few minutes later move onto the next panel, etc you might well be ok.

Cellulose isn't the easiest of paints to get a good gloss, but it has the big advantage that overspray dries in the air almost instantly so lands on next door's car as dry dust.

Slower drying paints are easier to get a good gloss but the overspray stays wet in the air for much longer, so lands and sticks to next door's car paintwork and windscreen while still wet, and it sticks! I'm thinking here of two pack paints, and also oil bound coach enamels.

I have always found that to get a good finish means having the right gun, with the right paint, thinned the right amount, with the right air pressure, at the right temperature, and moving the gun at the right speed. If you get a poor finish it can be tricky to know which of these variables you got wrong.

[Chris KC]

Thanks Both.

Ivor - yes, that's what the merchant said, also that once acquired I will probably want to do other things with it and the capacity will then be an asset.

Howard - the flip side of the above of course is cost and garage space, so it's good to know a smaller compressor can do the job, thanks. Workflow is going to be my biggest problem I think. In a perfect world of course I'd strip the car down to a bare bodyshell, but in reality I'm repairing her bit by bit and endeavouring to keep her on the road meanwhile (if intermittently), so will have to do things piecemeal, and with the car more or less fully trimmed. I need a functional finish at this stage rather than 'showroom'.

Yes, I learned about prep when I brush painted the Ulster! I would probably do the Box the same way, but enamel doesn't really lend itself to 'patch' application and I'm not sure how I'd manage all that wet sanding with the car in one piece. (I anticipate at least less of that with cellulose).

I'm fortunate here to be within 10 mins walk of a supplier for painting accessories and sundries, and a modest drive to Craftmaster Paints who I <believe> will be able to supply me with the paint.

---

Thanks Andrew. Yes, I'm pressed for space so what happens to airborne paint is an issue. I think I will have to hang dustsheets in the garage and work in the doorway.

I perceive the advantage of cellulose is however badly you put it on, it can be flatted and polished up...!

Understood about the variables. Compared with the cost of a pro spray job around here the investment in gear is easily justified so I will have no qualms about buying decent kit, the rest I guess is a learning curve...

[Reckless Rat]

I have a single cylinder 50 litre compressor and it was OK when we resprayed the wings on the RP a few yearx ago but it did run out of puff a few times. A twin cylinder compressor with a 100 litre tank will be absolutely fine.

[Hugh Barnes]

If working with cellulose, I think one of the most important aspects is appropriate choice of thinners. I believe it comes in 'grades' between 'fast' and 'slow' which reflects the drying time. Like my suggestions about repainting the lettering on an instrument panel, this is said with no actual practical experience of course...

(never stopped me in the past...)

[Chris KC]

Reckless - also good to know. Based on searches so far the 100L ones are not that much more than the 50L ones, so I may push the boat out. The main issue is going to be where to put the ruddy thing - perhaps I need to 'buy - use - resell'. 

Hugh - I was reading about that last night - I gather "top gloss" is the thing to ask for (though that might be American I'm sure it can be translated). The standard thinners are fit for washing equipment by all accounts. 
I liked your advice on painting instruments very much! And almost chipped in that Craftmaster do a lovely high-pigment signwriting enamel ('almost' because it's probably a bit OTT in that application).

[Charles P]

I use a 2HP 50 litre compressor to paint. You should choose a gun that is compatible with the slightly lower flow rates but it’s manageable. A remote regulator/filter/water separator is essential.
My compressor lives in the garage loft (I have a normal pitched roof space with a ladder) Much easier to keep it out of the way, even if getting it up there is no small task.

Charles

[andrew34ruby]

I perceive the advantage of cellulose is however badly you put it on, it can be flatted and polished up...!

Yes cellulose can always be flatted and polished back, so can 2 pack. But it can be a lot of work. And over the years it will need wax polishing more often.

With everything perfect, the amount of thinners recommended will be right. With a smaller gun you might need a bit more thinners, similar if the temperature is a bit low, or if your air pressure is a bit low, or if using cheap thinners. Yes the expensive top-coat thinners gives a better finish easier, but it costs a lot more.

Then you need to avoid runs. Knibs and curtains happen if the paint is too thin (too much thinners) but can also happen with paint not thinned enough. If you put too much paint on you will get runs. Too little paint and you get no runs but a rather dry, orange peel type gloss.

I found the best way with cellulose was to spray a panel with a thin coat, then spray it again straight away to give a gloss, then the same for each panel right round the car.