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Cratering of Freshly Sprayed Water-Borne Polyurethane Finish

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Forum topic by 1voyager1 posted 04-07-2016 12:05 AM 1154 views 1 time favorited 22 replies Add to Favorites Watch
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1voyager1

74 posts in 894 days


04-07-2016 12:05 AM

Craters [fish eyes?] are forming in the freshly sprayed w-b polyurethane finish I’m spraying onto my garage cabinet pieces.
A glue size was applied.
Then, a wood dye was applied.
The first 2 coats of polyurethane were applied.
A very few small craters did appear in the second coat application.
They were completely unnoticeable after the second coat dried.
I lightly scuffed the surface of the prior coat with a 400 grit sanding paper on a block, then wiped down with a dry terry cloth rag before the next application.

I had been operating the sprayer at its lowest settings.
It was taking multiple passes to get a reasonable layer of finish on the wood.
I increased the gun’s application rate, flow and air, a small amount on the third coat getting a better coating of paint in a single pass.

The third coat is not dry yet.
But, I am concerned that the cratering will now be apparent after this last thicker coat dries.

How to stop this from occurring?
Can it be repaired?

EDIT:
Now that the finish is drying, it looks as if there are many small blisters on one of the pieces.
Probably blisters instead of craters because of the thicker coating.
I’m wondering if the sanding without a thorough cleaning afterwards is the cause.
I used “3M Pro Grade Precision Advanced Sanding Sheets”.
They have what feels like what could be a silicone type coating on the back side.

-- Every mighty oak is nothing more than a nut that has stood it's ground.


22 replies so far

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OSU55

1056 posts in 1452 days


#1 posted 04-07-2016 02:32 PM

What brand of wb poly? Carrier used for dye, water, alcohol, other? It is good practice to wipe down the surface with 1:1 denatured alcohol and water before using wb finishes, and to use NON stearated sandpaper – most of the lube soaps dont play well with wb. Small pinholes can be caused by many passes to get film thickness and or a very dry environment, both allowing too qick of setup and the underlying finish outgassing. Heavier spray and a retarder help.

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BinghamtonEd

2281 posts in 1832 days


#2 posted 04-07-2016 03:37 PM

Not sure what your issues are caused by, but I just used the same sandpaper, in 320 and 400, between coats of Target waterborne finishes (HSF5100 and EM6500), wiped with the 1:1 water & alcohol after sanding, and noticed no adverse effects. I think the wipe down with the dampened rag does better than a dry terrycloth rag. It seems that the dust would stick more to the dampened rage, versus more just being pushed around by the terrycloth.

I’ll let someone with more experience answer the question about your cratering/blistering, but I just wanted to chime in that I’ve had no adverse effects with the paper you used, when thoroughly wiped after, at least with the Target finishes.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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1voyager1

74 posts in 894 days


#3 posted 04-07-2016 05:30 PM

Thanks guys.
After applying the 3rd heavier coat, the cratering looked so bad I panicked.
Now that it has dried over night, it doesn’t look so bad.
The craters are now just small circular flat finished spots scattered through a satin finish.
Although, some are very shallow, barely discernible, depressions to the touch.
What looked like an area on one piece that was blistering doesn’t look so bad now either.
But, I do want to correct what I’ve been doing wrong before I continue on.

I am completing one of the three cabinets before starting to finish and assemble the last two.
I want to get all the problems worked out.

I was wrong about the sandpaper’s backing.
It isn’t a silicone type, but a rubberized non slip backing.
It also can be used wet.
I’ll wet sand the finish on the pieces to remove the blemishes.
Being as all pieces are simply flat surfaces with no corners to deal with, rather than hand sanding with a block, I’ll use a RO sander.
That should make cutting the surface down to remove the blemishes easier.
Then, I’ll wipe with a water – DNA mix before applying the next coat.
I’ll probably use the terry cloth rags again unless advised not to.

Back many years ago, I spent a summer as the helper in the refinishing of the woodwork on a sailing yacht.
The memory of hand sanding all those intricate surfaces and corners still gives me nightmares.
That’s why I’ve chosen to apply the finish before assembly on this job.

EDIT:
Sorry OSU55, I forgot to answer your questions.
I’m using the Rust-Oleum Parks WB Polyurethane for Floors.
It comes in a plastic one gallon bottle.
Because I’ll be working in, on, around and out of these cabinets, I wanted as hard of a finish as I could get.
I assumed the floor application would give me that.
Plus, it was cheaper than the other WB polyurethanes available.
I’m so tight I squeak, so that is always a consideration.

The dye was a Transfast dry powder that I mixed into water a month or two ago.

Low humidity is not my problem.
I’m in Hawai’i with very high humidity.
I actually feel it is working for me by slowing down the drying of the finish.
It still skins up fairly fast, but is slow to completely dry.

-- Every mighty oak is nothing more than a nut that has stood it's ground.

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CharlesNeil

1610 posts in 3333 days


#4 posted 04-07-2016 06:07 PM

pm sent, email me,

Im amazed your glue size experts dont know the answer, they profess to,guess testing and long term endurance and chemist, as part of their experimentation were not part of the equation, I can and will help .

View upinflames's profile

upinflames

209 posts in 1624 days


#5 posted 04-07-2016 07:38 PM

I don’t see where glue sizing comes into play here…..but, THE glue size expert has spoken.

Could be a number of things, I won’t keep it top secret, others may benefit from the discussion.

Any way, too thick a coat, not dry enough between coats, Crystalac Fisheye remover works pretty good if you throw thick coats down, could be pulling away from the dye, that’s where the lighter coats come in.

Spray gun cleanup can effect the outcome, airline, if using a turbine it could be the heat.

Best to try any unfamiliar finish on scraps…saves lots of headaches

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CharlesNeil

1610 posts in 3333 days


#6 posted 04-07-2016 07:54 PM

WAG . WILD ASS GUESS. seems to be the know it all answer, they àre totally clueless. Unless you ask them. , c heck ou t their profiles, the have done nothing . Lmao , ignorance is an amazing thing specially when it can be hidden under fictitious names

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CharlesNeil

1610 posts in 3333 days


#7 posted 04-07-2016 08:17 PM

Up in flames,do you have Anything you have actually built and finished to show us , it gave a few (hundreds )

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CharlesNeil

1610 posts in 3333 days


#8 posted 04-07-2016 08:20 PM

Up in flames,do you have Anything you have actually built and finished to show us , I have a few (hundreds ),beat it 46 years or so and you ?

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upinflames

209 posts in 1624 days


#9 posted 04-07-2016 09:01 PM

I don’t do WAG’s, I go from experience, yeah I don’t put glue sizing in a can and sell it, I don’t do top secret crap.

I have 35+ years in this as a LIVING, not a hobby, IF I was full of baloney I really don’t think I would still be in business.

As far as “projects” , I don’t take a picture of everything I build, I don’t need to be patted on the head and hold hands and sing kumbaya.

Get over yourself and help folks HERE instead of in a cloak of secrecy…....

Need to cut the legs off your horse a little too….

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CharlesNeil

1610 posts in 3333 days


#10 posted 04-07-2016 09:09 PM

Then shut up and show us, curious minds want to see,

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CharlesNeil

1610 posts in 3333 days


#11 posted 04-07-2016 09:25 PM

I think you are an idiot who hides behind a key board and hasn’t a clue, just an ass hole who wants to be heard and no one is listening. Gave YOU NOTICED , no one responds to your post, that should tell you something. But again, here on LJ, we have dealt with it before, so don’t feel special .

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CharlesNeil

1610 posts in 3333 days


#12 posted 04-07-2016 09:50 PM

Than you sir. YOU have well established my point. However ,as with this thread, you and your coharts. need to step up to the plate and help and answer these folks who are using your glue size and having issues. BUT I suggest you do some research, so you know the answer.
We will all await how you handle the OP of this thread.
As stated, show us , help this guy out, no excuses .

View shampeon's profile

shampeon

1712 posts in 1646 days


#13 posted 04-07-2016 09:57 PM

Cool comment pollution, dick measuring. Very cool, very helpful.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

View Redoak49's profile

Redoak49

1947 posts in 1451 days


#14 posted 04-07-2016 10:23 PM

I was reading this thread to get some education. I think I will run for cover…

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CharlesNeil

1610 posts in 3333 days


#15 posted 04-07-2016 11:20 PM

Before you slam me too hard click on up in flames anything I say he tries to slam me , but uses a fictitious name, and has nothing to show, just runs his mouth, and I have had enough.
Haha , and I was being polite, won’t be next time , lol

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