Painting a piano, epoxy primer, 400 sand grit question

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danford1

I'm painting a baby grand piano for a piano gallery.
It has the ultras gloss polyester finish on it. I sanded that down with 400 paper and I'm ready to spray the SPI black epoxy on it. ( I plan to use black PPG DCC solid urethane over the epoxy).
My question is about the 400 sand paper. Will the SPI epoxy stick well to a 400 grit finish or do I need to use 180?
Danford1
 
The paper I used is actually P400 Norton, on a sticky roll.
I do have 180 if it would be better...

Danford1
 
danford1;24617 said:
I'm painting a baby grand piano for a piano gallery.
It has the ultras gloss polyester finish on it. I sanded that down with 400 paper and I'm ready to spray the SPI black epoxy on it. ( I plan to use black PPG DCC solid urethane over the epoxy).
My question is about the 400 sand paper. Will the SPI epoxy stick well to a 400 grit finish or do I need to use 180?
Danford1
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What was the condition of original paint you are going over? Do you need to fix anything in the surface? If the old paint surface is good and you sanded with 400 you could use the epoxy reduced as a sealer and for adhesion.
 
metalman;24646 said:
What was the condition of original paint you are going over? Do you need to fix anything in the surface? If the old paint surface is good and you sanded with 400 you could use the epoxy reduced as a sealer and for adhesion.
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The surface is smooth, flat and ready :) It had chips in it that I used the special polyester lacquer made for piano surfaces to repair them. I then block sanded the piano, it is very flat.
I didn't think of mixing the epoxy as a sealer, I was just going to put on the two wet coats of epoxy as per instructions, let dry, block flat and apply paint. Since I plan to block sand it, I think the thinned sealer coat would be to thin to block flat.
I know sanding isn't needed before paint but I want this surface super flat, no hint of orange peel in epoxy. It will be painted a very high gloss black and ANY imperfection will show up. I feel more confident blocking the epoxy flat.
Now, Let's talk about this. When I block the epoxy flat pryer to paint (solid urethane single stage DCC) , what grit should I use? My plan was 600 but if someone knows a better grit to use, please let me know.
Thanks

Danford1
 
If it were my piano and I wanted to make positively sure of the best results I'd let the epoxy cure up well before blocking, and apply a sealer coat before paint. Will that poly coating that's on it absorb solvent and become unstable, swell? A few coats of cured and blocked epoxy sure would put my mind at ease knowing solvent wouldn't reach it.
 
Bob Hollinshead;24700 said:
If it were my piano and I wanted to make positively sure of the best results I'd let the epoxy cure up well before blocking, and apply a sealer coat before paint. Will that poly coating that's on it absorb solvent and become unstable, swell? A few coats of cured and blocked epoxy sure would put my mind at ease knowing solvent wouldn't reach it.
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No, that factory poly coating is extremely durable. My friend has worked at the piano shop for 30 years. He says NOTHING the ever tried would eat into the piano poly. They tried Acetone, lacquer thinner, MEK etc over the years while working on pianos. I've sprayed SPI epoxy over the piano poly before with good results. I'm confident the SPI won't eat the poly.
moving on...
I sprayed on two coats of SPI yesterday on the P400 grit prepared piano :)
It has been over 12 hours now at 65 - 70 degrees. I haven't touched it yet but it looks dry. The only "issue" I have is what looks like exaggerated fish eye on a top edge of the piano. I'll post a picture later if I can. I used SPI water borne W&G remover. Perhaps I didn't rub it all off the rim or let it flash long enough before priming. It is easy to sand that area down and re-apply epoxy as I'll be spraying a few more coats of epoxy on the piano as I sand it down before paint.
Let's talk about a seal coat please. Why would I do that - in this case. What I mean is, I'll be blocking this thing smooth. If I spray on a sealer, I would be blocking that smooth as well because the just sprayed seal coat won't be as smooth as my blocked surface. Since I'm blocking before paint, what difference is there if I paint over blocked epoxy or blocked thinned epoxy? When I sand, I won't be sanding through the epoxy, just blocking the orange peel and dust out of it.
I can understand sealing a car where body filler or metal is exposed after sanding. There isn't any painted metal on this piano.
Do I really need to spray on a thinned seal coat of epoxy? As mentioned. I would block that before paint anyways.
Thanks.
Please keep the info flowing. I enjoy learning all I can.
Danford1

EDIT: Here is a link to the project pictures. I will be updating this a couple time a week.
http://www.flickr.com/photos/14256847@N08/sets/72157631686472491/
 
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The fish eye looking thing happens sometimes when the epoxy is applied too heavy especially on the first coat. If you let the first coat flash well, 30 min. to an hour depending on temperature, it won't happen on the second coat unless you do have contamination.
I agree with Bob's advice to let the epoxy cure all the way (7 days should do it), that with be a guaranteed stable base for your top coats.
That said, once epoxy is fully cured nothing bites or sticks to it other than more epoxy. You would only have a weak mechanical bond between the top coat and the epoxy and the finer the grit used to sand the less that would be. An epoxy sealer puts back the adhesion, it bites the cured epoxy and your top coat will bite the fresh sealer. Try mixing the epoxy 1:1:1 with slow reducer and spray a test on something else. It should lay out flat as glass and not induce and orange peel or texture unless you spray it poorly. Top coat should be applied after flash, 15 min. to an hour is what I wait, others may vary on that but you don't let it go overnight or longer. The SPI epoxy is a great product and it is very versatile but you need to understand how it works and get used to using it.
 
I let the first coat flash about 50-55 minutes before I sprayed the 2nd coat. The fish eye looking areas were in fact sprayed on thick as the gun was to close to the surface when applied. Easy enough to sand down and redo in this case.
Waiting a week for the full cure is possible IF I don't have to keep the garage heated very warm during that period. I have the other side of parts to squirt epoxy on and while I'm doing that, the garage will be 65 -75 degrees (1 to 2 days).
I can maintain it at 50 degrees for a week if that is OK. Then I'll have to heat the garage and parts back up to shoot the top coat.
Danford1
 
Barry would be the guy to ask about cure times at what temperatures. The way I figure any paint's stated dry or cure times is at about 70 degrees. I believe the cooler it gets the slower it cures and heat speeds it up. I try to keep that in mind when working with the epoxy's "7 day window", so if for example I put parts out in the sun (the Indian heat lamp:D)for the good part of a warm day and the surface averaged 120 degrees, the epoxy is pretty much cured. At that point if I'm ready to finish sand and paint I will use epoxy as sealer to insure good adhesion.
I don't know at what colder temperature epoxy goes dormant or if that is even possible.
 
I read earlier where if the epoxy sands and leaves dust, it is cured. I sanded some of it today and it left some dust, but also clogged the paper so I know mine isn't fully cured after just 18 hours.

Today I turned up the heat to 75 and prepped more parts. I just sprayed on a coat of epoxy and as I write this, I'm waiting the required 30 plus minutes for flash time before the 2nd coat goes on. I can easily wait an hour today :)

Danford1
 
Give it some time, let it cure, you want the best results but you're rushing the sanding IMO. I wouldn't let the heat fall below 60*. Adhesion of the single stage black on cured sanded epoxy will be ok but it would be even better with a sealer coat of epoxy. It's a piano, so it probably won't get rock chips-LOL so maybe not worry about the sealer coat.
 
If you are gonna cut and buff the top coat I would not worry about peel in the epoxy sealer coat. Make sure you get 3 good color coats minimum. If you are gonna rush it along and not keep the right temps look out for more problems some now or some later maybe...esp using epoxy.
 
Bondoskimmer;24816 said:
If you are gonna cut and buff the top coat I would not worry about peel in the epoxy sealer coat. Make sure you get 3 good color coats minimum. If you are gonna rush it along and not keep the right temps look out for more problems some now or some later maybe...esp using epoxy.
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I have kept the garage 70-72 degrees the entire week. I'm letting the epoxy set up for 5-7 days before top coating. I sprayed the first top coat of black today after sanding the epoxy I sprayed last Monday (7 days ago). I used P400 paper and wet sanded it. I used SPI water borne W&G remover and let it dry a good 1/2 hour before spraying. I'm using PPG DCC solid urethane. I have a long way to go before it is done but I'm enjoying the project :).
Danford1
 
I seen the pics and I am intrigued. Can't wait to see the final results. What kind of gun are you using?
 
Bondoskimmer;24841 said:
I seen the pics and I am intrigued. Can't wait to see the final results. What kind of gun are you using?
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I'm using a Devilbiss GFG-517. It is an old gravity feed gun I've had for about 12 years. It Always worked great for me, I can't see the need to buy another gun...

Now, I've got a paint speckle issue. I'll post it in the top coat area. I'm getting thousands of tiny specs in the finish. They appear as soon as sprayed like they were mixed in with the paint. Check the top coat area for the post.

Danford1
 
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