7008 user's... help!

[Harry72]

I've been trying to put 7008 2pac poly on my new kitchen bench tops... and its turning out real
The 7008 is being applied by spraying, the problem Im having is the jarrah has very fine hairline cracks which you cant see or feel before the finish is applied.
It seems that the 7008 has a strong surface tension which prevents it from flowing into these cracks, it just sits on the edge of the cracks... making them look huge and stand out like(you probably know the saying).
I dont want to grain fill these cracks, as I know when I've done it before during summer, when winter ends the jarrah raises the filler because these benchtops in parts will see direct heat from the sun.
The 7008 seems to be too thin(without thinning) when mixing compared to normal poly, doing the drip test it breaks at about 6~8cm whereas I normally thin down poly to a 10cm break point? I use a 1.4mm nozzle on my gun, its only a cheapy scorpion gravity feed job, I've had good results with it on numerous occasions poly/acyrlic and lac's, its not as good as my samson S90 but good enough for wood.

I've tried using the 7008 straight from the can, tried it thinned 10%, tried varying the thickness of application and varying the gun settings(flow rate and fluid rate).
The only thing I can think of is the high humidity we are currently experiencing in this area?
Doesn't seem to make any difference what I do, what gives? I've never had a finish frustrate me like this before!

Durwood, any ideas mate?

Just went down the shed and took some pic's, now I gots the spots too

[johnc]

I've used epoxy in the cracks on red gum and a bit of darkened filler on the fine, looked invisible when finished.

[Harry72]

Yep this has too...

[journeyman Mick]

Harry,
it looks to my relatively inexperienced eyes as if you need to thin the first couple of coats more. This will reduce the viscosity and hopefully surface tension enough that it will flow into the cracks rather than pull back from them.

Mick

[Harry72]

Yes I thought that too, I've only thinned the fist coat tho.
I dont think I'll have enough paint left to start over again(its been stripped back twice already). I may even just go back to Cabots cabothane, always had good results with that.

Wattyl recommended not using any sanding sealer, only to use putty like timbermate to grain fill but I've no luck with filler before in this situation.
My last idea is to heaven forbid... "brush" on a heavy coat and force the paint into the hairline cracks.

[rod1949]

Its been a fair few years since I used 7008 on some fine furniture but yes I can relate to you problems.

I assume you want an unblemished glass like finish? The 7008 will give you that but requires a bit of work to achive.

What I did:
After an initial couple of spray coats and cutting back between coats it was obvious the channels required some additional attention so rather than spray I poured and or poked 7008 into them and let dry throughly cause if I didn't it would just pull out when cutting back. Cutting back between each coat so it has a completly white sanded finish, which reveals any imperfections. Fine dust in the air was a problem but eventually I achived an un-blemished glass like finish.

I cut back using wet and dry carbourendem paper (wet). The aluminium oxides weren't around at the time.

I note in your pictures it appears you have minute air bubbles, you need to let the 7008 mix stand for a while before spraying.

Goodluck

[Bob38S]

Yes I thought that too, I've only thinned the fist coat tho.
I dont ..........................
.
My last idea is to heaven forbid... "brush" on a heavy coat and force the paint into the hairline cracks.

Not so sure that this last idea may be a totally bad one and needs to be rejected out of hand.

If you can get it all filled by brush is it possible to then sand it [probably heavily without going through the coating] and then spray it.

Seems a tedious way of doing it and, not having done I can't say it will work, but if this is the stuff you really want to use then perhaps this could be a way to get it to work for you.

Just a thought,
Bob

[durwood]

One of the basic rules of painting is :
you should never spray the first coat of any finish into wood.

What is happening is that when the air from the gun gets to the surface it hits the cracks/ holes /open grain etc and creates a high pressure pocket as it bounces back.

You should always brush/pour rub the first coat onto the timber that way you can work the material into the low areas and fill them up. If they are really big or deep you may have to do it a couple of times. If the timber isn't properly seasoned it may shrink more after you paint and sealing it with a coating won't stop it shrinking more.

As you want to only have the clear finish on the timber without filling there is no issue with rubbing it in first.

Anytime you paint timber if you intend finishing with a spray gun brush the pink primer or what ever on first. If its a hard close grain wood thin the coating down so its really thin and can soak in.

You could have also used a brush to rub the Estapol in after you sprayed it but if its a hot day it might set up too quickly to alow the brushed area to flow out as well as the surounding sprayed areas. It's alway best to have a flat fault free surface before you spray so it can achieve what you want.

Any surface that has faults in it that allows the compressed air to bounce back out will leave you with a faulty finish. Often some paints applied badly get pin holes in them. You can spray on as much as you like and they won't fill but if you manually rub the wet finish in with a finger you can use your coating to fill the holes/cracks.


Like rod1949 suggests fill them.
Give it a rub back to remove the gloss and mix up a small amount and set about filling any low spots. If the cracks are deep see if you can first apply a thin coat to soak down into the cracks and then use thick stuff to fill up to level when you can sand them down so the whole surface is flat then one good coat (even a thin one) to regain the gloss and you should get the surface you want.

[Harry72]

Thanks guys, I give it another(again! ) rub back and try and fill each crack with some thinned out to 15~20%, sand flat then recoat.

Dunno about the surface faults Durwood, hairline cracks I could not see them or feel them... the surface was good enough to spray auto acrylic with!(I've done a few cars and plenty of painting of car audio fibreglass parts... and lots of poly on wood before)
Thats why I thought it was surface tension? At first I thought it was reacting with the epoxy filler I used, but in other area's it hasn't effected it.

Problem I got now is I have no sanding disc's left and they cant be obtained in my town(typical)... time to call me mate Ray at Elraco's!