automotive clear on bamboo backed bows

[Swanny in MD]

Anyone else putting this stuff on these?  

I'm having trouble with tiny air bubbles being caused by dry heat in my shop after I spray and let it tack off.  If I keep the heat below 70 they won't appear, but anything above, especially forced hot air will cause them to come out like a plague.

Funny thing is they never appear on the raw boo backing...

My guess is the heat is causing the wood cells to expand and let out air.

I though i've read folks putting heat lamps on them after each coat, but even these cause bubbles for me.

Any thoughts to what I could prevent them....like some other sealer for first coat?  As I'm writing this I just thought of heating up the bow with a heat gun a bit before I spray?

I only put two coats of clear...don't know why others put 7 to 9 when you can get the second to look like smooth glass.

[vermonster13]

Automotive clear tends to flake from all the bows I've seen of late. It is'nt made for the amount of flexing a bow does. Gary Sentman uses it and the finish in the two bows I got of his both flaked and peeled badly. One was brand new, the other 6 months old.

[Bandit46]

Ken; Sounds like "fish eyes" in the clear. Jack Harrison had a friend who helped him fix that problem (the fellow worked for the paint company that Jack used) He gave Jack an additive that eliminated them in the finish, when mixed in the paint. I believe that Jack used PPG Automotive clear. The article was in the Bowyers Journal
Magazine. Ken, also, check with the paint manufacture to see if you can add FLEX to the clear. This is used on the Composite 5 mph bumpers to keep the paint plyable and flexible, and I thnk it will work with the clear too.

[ethan]

Ken, if you put on a heavy enough coat you can wet sand the spots out.  It will nock alot of the shine off to leaving more of a flat finish.

[Swanny in MD]

Thanks for the thoughts.  

Lots of variables as to why it's flaking on a bow...from prep to product to application to mil thickness. I've done about 8 bows in it and haven't had the problem, and haven't used flex additive either.

If it does flake due to flex...it should only appear in the high stressed areas.  I wouldn't doubt folks are putting too many coats on....standard in auto industry is two to three coats.

Prep with 320, clean with lacquer thinner, tack off, light first coat to dry, then heavy second coat with a bit more hardner in the clear than first coat.  Wet sand and buff if you like, but i haven't needed to.

The stuff I'm using is about 1/3 the price of PPG's product.  Used it on alot of customer's vehicles and haven't had any complaints or redo's.

I've used the fish eye product (been spraying basecoat/clearcoat on cars and trucks since 1988) and I am absolutely sure I don't have fish eye.  Fish eye is caused from oil or grease underneath the finish...you can see fish eye right after you lay a coat on as the clear won't cover and hold on the spot.  

These aren't water spots either.  They appear in teeny bubble form and grow bigger...I can pop them with my finger...so I know they are caused by released air underneath the surface.

I'm going to try a different sealer for the first coat on the next and see what happens.

[DarkeGreen]

Don't take this as fact because I do have a clue. I seem to recall reading about this issue somewhere as the "fix" was to heat the bow in a heat box first. That openned the wood grain and let the air out of the pours so when you sprayed the bow it was cooling and not releasing air in to the finish. Maybe this will jog someones mind and they can let you know if it is a real solution or not.

[Swanny in MD]

That sound viable, DarkeGreen.  I'm going to try that as well.  It would make sense that this problem doesn't happen on fiberglass or metal since the cellar structure is different.

[Dave Worden]

Ken, I'm just about to ask the local bump shop to clear coat a bow I just built.  It has bamboo lams under the glass, only the edges show.  Will they bleed this air also, or is this just a problem when they are the outside lams?  Any hints I should tell the guy at the shop?  
Thanks,
Dave

[AkDan]

Darke has it spot on.    The easiest way to get rid of those bubbles it to get it warmer then your shops temp, and spray while it's cooling off.    Some of this also depends on the type of finish you're using how much heat to use or if you need to apply while tacky on additional coats.   Sure beats the sanding!!!!

[arraflipper]

Ken,

The PPG products work very well over Bamboo.  You can put super glue over the places that are causing problems before you spray.  On the first coat I put it on very thick to the point it wants to sag.  I hold the bow while spraying and twist my wrist up and down, to keep the sags from becoming runs.  

I use two parts of clear to one part flexiblizer, one part hardner, and one part reducer.  I put one coat on, when it is very tacky I apply another, for a total of three coats.  Then sand with 320 grit, after the third coat dries, I do this three times then polish it out.

Jack Harrison's main problem was he was not using measuring cups made for spraying.  The cups he was using had a film in them that caused most of the problem.  PPG makes cleaner to use before you spray, with clear finish.  

It works well, is a very durable finish that gives you an UV protection, in the finish.

[Swanny in MD]

thanks for the info, Jim.  

"I hold the bow while spraying and twist my wrist up and down, to keep the sags from becoming runs. "

So, are you starting at both ends and working your way to the middle while your hand is holding the handle, then hang it and finish the handle area?

I seem to like string it up (small gauge wire around string nock connected to thin string) in front of my exhaust fan and twist it up a little, then as it spins slowly I start from top...spray on single directional course to bottom and go back to top....bow is just about done spinning.  Finish is very consistant with no runs.

What's your thoughts behind so many coats and efforts to wet sand?  Have you ever measured how thick your final coat is?  

From my experience with automobiles...the thinner mil thickness (to a degree..normally two coats) equates into a tougher finish.  It would seem I could achieve a 'world-class' (looks and durability) finish with only three coats of clear, wet sanding followed by buffing.

[ethan]

Ken, the guy who got me my info on spraying auto-clear does body work to.  He also said no matter what, don't put more than 3 coats, 2 would be better. Maybe you've hit the nail on the head as to why some coats are chipping.  I've never had a problem either.

[arraflipper]

Ken,

All my handles are wrapped with leather.  I spray the handles three times just to seal the wood.

I have never checked the mill thickness when I am done finishing the bow.  I like the added depth the extra finish gives the bow when polished in the end.  I have never had a problem with the finish chipping.  I have had a couple get scratched when I let someone try them.  It was an easy fix by polishing out the scratch, when the bows were returned.

I don't wet sand till the final coat is dry.  I sand with 320 grit or scotch brite in between coats.