Spraying Thunderbird

[Walt Francis]

Okay, I have read and researched every thread I can find on spraying Thunderbird and still can't get it right.  Maybe somebody here can figure out what I am doing wrong.   I have been using the following procedure and end up with pinhead sized craters everywhere in the finish.  The bow finish, when sprayed onto the bow, never lays down or smoothes out.   My setup:

1.   Equipment
  •   VLP air gun
  •   Three air regulators
   o   1 at the compressor (set at 120psi so it doesn’t cycle much during the spraying)
   o   1 after the water filter (set at 44 psi)
   o   1 at the gun ( set between 30-42 depending on where I get the best coat on the test wood)
 •   One water/moisture filter half way between the compressor and the hose (I run a coiled 50’ hose from the compressor to air filter and then another 50’ hose from the filter to the gun)
 •   Portable Spray Booth with air filters and exhaust fan (really good circulation so over spray or mist is not an issue)
 •   Good mask/filter-so the odors are not making me loopier then I already am

2.   Thunderbird
 a.   Mixed one part 10 mil) A to one part B (10 mil (measured with syringes , so the mixture is dead on))
 b.   Let set for 30 minutes per directions
 c.   Thin with Thunderbird thinner (varies, tried 10mil and varied it +/- 5mil for there)
 d.   Test spray on piece of wood, usually same type as the riser and it looks fine

3.   Preparation
 a.   Sand wood parts to 220-440
 b.   Sand glass to 600
 c.   Air off the entire bow
 d.   Bow is hung from the top tip and is not touched  after being cleaned
 e.   Clean entire bow with denatured alcohol

4.   Application
 a.   Spray form 8-16” (tried these distances and everything in between) with a steady, continuous,  movement and distance of the spray gun.
 b.   Spray, starting above the top tip of the bow and continue past the bottom tip
 c.   Riser section is sprayed using the same method as above.

5.   Results
 a.   The finish lands on the glass and the craters form immediately
 b.   The riser doesn’t look bad at this point but develops pinhead sized craters before the next application (2 ½-3 hours)
 c.   When the finish hits the bow there are white, pinhead sized spots everywhere
 d.   They stay white for about twelve hours before turning clear.
 
Final analysis:  Looks like $#!t

Getting tired of the old routine of spray on, sand off, spray on, snap off……….  In case you can’t tell I am extremely frustrated with this finish.      Any constructive suggestions would be appreciated.

[milehi101]

One thing I have found is water in the air lines can be a major problem. If your humidity is high I sure would check that.  Also I put dryers in the water line andchange them at the 1st sign of what you are experencing. It may not be your problem but I have had similar problems with finishes and it is water that causes the white spots.

[Walt Francis]

Hal, thanks for the response.

The local moisture is high, it been raining/snowing a lot the past couple of weeks.  So that may be the problem.  Moisture is why I bought the moisture filter, it is new, strait out of the box.  Bought it from an auto paint supply store and they felt this would take care of any moisture.  However the air hose has been used for years on my finish guns without a filter, the moisture may be from that.

What are dryers in the water lines?

Anybody know of a good method to dry the inside of an air hose?

[Brandon Stahl]

[Bert Frelink]

Walt,
A couple of questions come to mind when I read your post.
What are you mixing the T-Bird in, I can remember years ago Jack Harrison had a problem with this and it was the wax in the Dixie cups he was mixing his finish in.
There are different strenghts of denatured alcohol use the 99% pure one, the non medicinal ingredient in this is water, if you are using the 70% you're rubbing 30% water on your bow.
Hope you figure this out, please let us know.
Regards.
Bert.

[critter69]

What Bert said, I had same problem with alchol. Then used the thunder bird thinner to wipe down with and have not had problem sence.

[Blkbird]

[GREG IN MALAD]

Walt,
Mix up some finish in the usual way and brush it on a piece of glass, if it doesn't crater then the problem is in your spray system.

This is my process for spraying Thunderbird epoxy. I sand the entire bow with 220 grit aluminum oxide, then wipe it down with acetone. I wear non-powdered latex gloves to clean the bow and never touch it with bare hands after that.
I pull the finish from the can with metal scoops(one for each part) and mix the finish in a glass pyrex measuring cup. After 30 minutes I thin it 20%.
I'm using a gravity feed automotive spray gun and an oil free air compressor set at 40 psi with one water seperator.

I have had my share of issues with Thunderbird but once I figured out the problems it works great. I would recommend trying a different way of mixing the finish. Either the syringes or the mixing cups could have oil on them. Also, T-bird seems to be temperature sensitive. Too cold and it sprays on chunky and takes a long time to cure. Too hot and the thinner will leave bubbles when the finish is cured.

[Walt Francis]

Everybody, thanks for the responses, you have brought up a few thing I haven’t considered.

Brandon:

“If you're getting white spots, that's usually a sign of moisture in the airline (from the air compressor).”
I think the trap/filter is doing its job the white spot diminished and eventually stopped by mid way through the second coat.


“Some or most of those inline dryers use silicon beads to pull out the moisture, however, the silicon particles can also contaminate the air in the hose and cause cratering in some finishes.”  
No silicone in the filter trap, at least it is not mentioned in any of the product information or the replacement filter.


“The best way to get rid of moisture problem is to use a HVLP turbine system. This is what I did several years ago. I got tired of fighting the issues caused by using an air compressor to spray with. I currently use a FUJI system and will never go back to using an air compressor.”
The Fuji system looks nice but the cost doesn’t fit my budget…..yet. Much more frustration and I will make the budget fit.


“The cratering can also be a result of other surface contamination.”
The surfaces are clean.


“You might want to try wiping down with acetone instead of denatured alcohol.”
I will try acetone next time, went away from it because of the fumes, but they are not any worse than the Thunderbird.


“Also, make sure you don't use any silicon carbide sanding paper. This can cause surface contamination and cratering with 2 part epoxy finish. Only use aluminum oxide and you really don't need anything finer than 320 on the glass before you start spraying.”
I am thinking this may be the problem.  Do not know what type of paper I have been using, silicone or, aluminum oxide.  The paper doesn’t say on it and neither 3M nor Gator Grit tells you how to tell the difference on their web sites. Anybody know how to tell the difference?


“Also, no steel wool in between coats. Steel wool has oil in it that can also cause contamination cratering. Use 400 or 600 AO or fine scotch brite pads between coats.”
I haven’t used steel wool for a long time, it also causes red/orange specs when pieces in-bed in the wood grain and then rust.


I don't know if any of this info will help, but best of luck in the future


Bert:

“What are you mixing the T-Bird in, I can remember years ago Jack Harrison had a problem with this and it was the wax in the Dixie cups he was mixing his finish in.”
Read that in Jacks book, I use a 3 oz. shot glass/tumbler.

“There are different strengths of denatured alcohol use the 99% pure one, the non medicinal ingredient in this is water, if you are using the 70% you're rubbing 30% water on your bow.”
I am using the 99% type.


Everybody, Thanks!! Your input is greatly appreciated.

[Walt Francis]

Greg:

“Mix up some finish in the usual way and brush it on a piece of glass, if it doesn't crater then the problem is in your spray system.”
Good Idea, that will help isolate some of the problem, or problems.


“This is my process for spraying Thunderbird epoxy. I sand the entire bow with 220 grit aluminum oxide, then wipe it down with acetone. I wear non-powdered latex gloves to clean the bow and never touch it with bare hands after that.”
Like you, I do not touch the bow after it has been wiped down.  However I haven’t been wearing glove.


“I pull the finish from the can with metal scoops(one for each part) and mix the finish in a glass Pyrex measuring cup. After 30 minutes I thin it 20%.”
I have been thinning it about 30%. Your humidity in southern Idaho is close to ours in Bozeman, I’ll try reducing it less.


“I'm using a gravity feed automotive spray gun and an oil free air compressor set at 40 psi with one water separator.”
Close to my setup only I use an HVLP gun


I have had my share of issues with Thunderbird but once I figured out the problems it works great. I would recommend trying a different way of mixing the finish. Either the syringes or the mixing cups could have oil on them.
Cleaned both with denatured alcohol. Next time I will use Acetone.

Also, T-bird seems to be temperature sensitive. Too cold and it sprays on chunky and takes a long time to cure. Too hot and the thinner will leave bubbles when the finish is cured.
The bubbles happened last time I sprayed Thunderbird (put a milk house heater in the booth to maintain the temperature.)

WOW!  There are still a lot of variables I need to isolate and remedy before spraying another bow.  Think I will use the better portion of my 2 quart Thunderbird working them out.

Thanks!