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Author Topic: Painting the frenchy-bus (longish)  (Read 4121 times)
buddydawg
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« Reply #15 on: July 03, 2012, 05:02:23 AM »

If you are going basecoat/clearcoat you are gonna have to prime.  Basecoats are relatively transparent and do not cover existing muticolored paint jobs nor will they bond well straight over bare metal.  Without going in to excrutiating detail I will give you a few suggestions:

1. Sand
2. Mask
3. Prime
4. Base
5. Clear

I think with out priming you are setting up for disaster.  I painted my bus outdoors and epoxed primed over all repairs and previous paint jobs etc.  The epoxy primer covers and sticks to everything and I have had no lifting or any other issue yet. 
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« Reply #16 on: July 03, 2012, 05:59:04 AM »

As well as potential reaction / adhesion problems, it's also much cheaper to use primer. Primer itself is relatively cheap (compared to top coat), and will also greatly reduce the amount of topcoat you need to apply to get coverage.

But the advise you had from your paint supplier is probably better and more valuable than any reply here from me or anyone else.


Jeremy
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« Reply #17 on: July 03, 2012, 06:21:29 AM »

As well as potential reaction / adhesion problems, it's also much cheaper to use primer. Primer itself is relatively cheap (compared to top coat), and will also greatly reduce the amount of topcoat you need to apply to get coverage.

But the advise you had from your paint supplier is probably better and more valuable than any reply here from me or anyone else.
Jeremy

Well - they may have a vested interest in selling me some more (expensive) paint but they have to make a living too.  And no metal, bare or otherwise, to be painted except for the black window frames and they're getting Tremclad. 
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R.J.(Bob) Evans
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« Reply #18 on: July 03, 2012, 06:42:31 AM »

Perhaps the term 'primer' implies a treatment given to bare metal, and 'undercoat' would be a better name for it when it's applied on top of existing paint or fibreglass (I assume you meant fibreglass when you said 'plastic' before incidentally - just to confuse things, painting plastic requires it's own set of specialist primers).

Some 'between paint' type primers are referred to as 'sealers' because they are specifically used for preventing reaction problems between the old and new paint. This isn't often a problem with base/clearcoat systems because they are pretty innocuous things, but two-pack paints for instance can be a very chemically intolerant. I've had reactions so bad that they've melted the fibreglass gelcoat - any thoughts of trying to save money by skimping on the primer stage seem a bit silly once you've experienced that kind of painting nightmare.

Jeremy
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« Reply #19 on: July 03, 2012, 07:13:30 AM »

Prevost converters order the shell painted or primed and then do the graphics or paint

 I watched Country Coach paint the graphics on the painted shell for years then clear coat so who knows
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« Reply #20 on: July 03, 2012, 08:53:39 AM »

Red is a very transparent (and expensive) color.  Best to primer to fill and smooth your bodywork.  Next sealer to provide a uniform color base.  Then base coat with final color.  Add stripes, flames, etc. and clear everything.

Since you have already painted color and have some bleed through from the existing stripes.  This new paint will act as a sealer for the next color coat.  So, wet sand the red with 400 and recoat for your final finish.  

I'm not sure why you were taping 2 hours after your sprayed.  Understand you were doing a test, but the paint should at least dry overnight before taping to presumably to add stripes.  

If the paint is so dry and hard after 2 hours, then I'm thinking you are painting when it is too hot and using a fast reducer, and possibly too much hardener.   This will result is dry spray areas that do not blend together with each overlapping spray pass.   Also increases the orange peel if the paint is not allow to flow.  They make different speed of reducers to better match your temperature.   Slow for hot days, and faster for the cool ones.  

Each coat should be a full wet coat.  Not heavy or too much that it will run,  but enough material.  Have your local body shop buddy show you.  Paint is too expensive to learn by doing, and doing, Wink  !  

Good luck and have fun.
« Last Edit: July 03, 2012, 09:06:00 AM by Hobie » Logged
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« Reply #21 on: July 04, 2012, 02:13:59 AM »

yes.. it should be completely primered first. depending on the color or colors used, ya might want to get the primer tinted the color of your base coats, but if its just red then red primer me guesses.  when i want to do a good paint job, i get the primer tinted and use the good paint at the industrial finishes place.. and red is really high now.

however, i didnt want to spend over 2k for supplies for my bus, so just used grey primer behind the silver and blue...
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« Reply #22 on: July 04, 2012, 08:58:23 AM »

Bit more on primers.  There are two types of primers.

Primer Surfacer - This is thicker and is designed to fill small surface irregularities and has to be sanded.  For example, to fill sanding scratches in bondo.  The epoxy two part primer has great filling ability and it sands easily. 

Primer Sealer - This is used after your body work is finished.  It is very thin and sprays like paint.  So watch for runs.  This can be tinted and provides a uniform color for the base paint coat. 

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« Reply #23 on: July 04, 2012, 10:28:22 AM »

And to add:

Etch Primer - Has acid in it which slightly eats into the surface being painted, to improve adhesion. Regarded as essential on aluminum and galvanized steel, and desirable as a 'first coat' on anything. The primer I use for everything (simply because I like it) is by Upoxy and is a 2-pack high-build etch primer, so 'ticks all the boxes'. It's good stuff. My local supplier stopped selling it at one point because the price went up and (he told me later) practically had a riot on his hands when all his regular customers found out.

I don't know whether the acid used in etch primer is Phosphoric acid, but if it is I assume etch primer must have some anti-rust properties as well. Phosphoric acid is the active ingredient in all those proprietary anti-rust paints (Hammerite, Rustoleum, POR-15 etc). Bodyshops used to have bottles of concentrated Phosphoric acid to hand, and before painting would wipe bare metal down with a rag soaked in the stuff. I believe they aren't allowed to do it any more because of health and safety rules.


Jeremy

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« Reply #24 on: July 04, 2012, 11:45:26 AM »

Bob, this is just to slow. You are lucky to have me here to watch out for you.
Now set up 2-4X6 posts at 10 ft apart, make sure you have an 42 foot on each side of the posts. Now nail a 2x4 across the top. Hook up a spray gun on each side and 2 at the top. Connect all hoses together and then a 2 inch air line back to the compressor. Now have someone pull the triggers that could be hooked together also with cables and return springs. They pull the triggers and you drive the bus through at an even speed about 40MPH. Then back up and put someone on a graphics-trampoline on each side and give them a spray-gun with another color. Set them to jumpin and drive through again. Instant Design.awesome!!!... Also you might want to tape up windows etc. too. That part is your choice?... Done
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« Reply #25 on: July 04, 2012, 11:52:16 AM »

Bob now I know what you were saying lol
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« Reply #26 on: July 04, 2012, 12:51:11 PM »

Bob, this is just to slow. You are lucky to have me here to watch out for you.

............. etc.


I can go one better than that Dave.  You guys don't have Red Green down there but some of you have likely seen him on PBS.  He's my hero - master of duct tape and innovator extraordinaire.  His conversion of a Cadillac into an excavator is one of my all time favorites.  One time he built a fence painter & I don't know why I didn't think of it before I started because it would have worked for what I'm doing.

The fence painting machine started life as a wringer washer.  The pump got repurposed to become a paint pump and he mounted some spray nozzles on the outside of the tub (with duct tape) at the appropriate heights to spray the boards on his fence.  Then he ran a rope from one end of the fence, through the wringer and tied it to the other end of the fence.  Dump the paint in the tub, turn it on, crank down the wringer and stand back.  Like Red says "if the women don't find you handsome they should at least find you handy"

The wind is blowing pretty good today but on the plus side not too many bugs can fly into that kind of headwind so I put another coat of red on.  I must be getting better at laying on a thick coat because today I got some sags and runs.  Gotta do some books this afternoon and then I'll sand the runs out tonight.  I'm just about ready for the next colour.
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R.J.(Bob) Evans
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« Reply #27 on: July 04, 2012, 12:59:23 PM »

Bob,  like others have mentioned you typically need to prime your repaired areas.  This is done to prevent outgasing.   You need to make sure that you have enough cure time with fiberglass.   A sandable primer is strongly recommended.   

For the other areas of the bus where you have just sanded the original paint it is strongly recommended to use a sealer.   You can call it a primer sealer.   The product that I use is manufactured by PPG   DP series..  Like DP 40, DP 50.  It is a two part epoxy sealer.   It is NOT sandable.   It is designed to seal everything under the paint and allow great adhesion of your new paint to the previous paint and repaired surfaces.   

Without doing this you risk adhesion problems.
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« Reply #28 on: July 04, 2012, 01:06:28 PM »

Bob, if the paint blows off you're driving to fast, slow down and paint it again. Hope to see you at the Brandon get together, we should check with Donna on it...
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« Reply #29 on: July 07, 2012, 01:33:01 PM »

You're right Clifford - there's a reason I waited to 'fess up about what I was doing.  On the other hand, one of the neat things about this hobby of ours is how people will just phone you out of the blue.  I haven't experienced that on the boating side but it definitely happens in the bus world.  Yesterday I had a great visit with Van.  I'm not following all his advice (mainly because I'm lazy) but I think he has forgotten more about painting than I will ever know. 

Yesterday I got the main colour on the curb side as well as the clear.  Today is a slow day - I masked for my gray stripe which is relatively small as well as my graphic on the rear which while somewhat intricate is a small surface as well.  Now I have to wait for all that to harden and then tomorrow will be another big day.  Fortunately Marilyn was in the big city so I could order additional paint and clear.  I don't know what the regs are in the US but up here its impossible to ship paint on a major courier.  I thought for sure it could go on the bus because they used to take anything and everything, including live chickens but it was going to be a 7 hour round trip to p/u more paint if it hadn't worked out that Marilyn was already in the city.

If anybody is interested I have an update here

For those of you that insisted - contrary to the advice I have received from a well respected body supply shop - that I absolutely needed to prime ......... you may be right ............ the paint may all fall off within weeks or even days ......... its just too soon to tell right now.  I disagree that I needed to prime to cover the previous graphics - I thought that initially but that was pretty well all beginner technique.  The red is definitely harder to cover with but by no means impossible.  What I did run into that a primer may very well have helped with was that the texture of the graphics showed through in some spots.  Particularly on the road side for some reason I had to do a lot of additional sanding after I thought I had already done a lot of sanding to get rid of the imprint of the underlying graphics. 
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R.J.(Bob) Evans
1981 Prevost 8-92, 10 spd
My website
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Simply growing older is not the same as living.
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