# Cratering of Freshly Sprayed Water-Borne Polyurethane Finish



## 1voyager1 (Jun 24, 2014)

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.


----------



## OSU55 (Dec 14, 2012)

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.


----------



## BinghamtonEd (Nov 30, 2011)

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.


----------



## 1voyager1 (Jun 24, 2014)

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.


----------



## CharlesNeil (Oct 21, 2007)

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 .


----------



## upinflames (Jun 24, 2012)

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


----------



## CharlesNeil (Oct 21, 2007)

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


----------



## CharlesNeil (Oct 21, 2007)

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


----------



## CharlesNeil (Oct 21, 2007)

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 ?


----------



## upinflames (Jun 24, 2012)

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….


----------



## CharlesNeil (Oct 21, 2007)

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


----------



## CharlesNeil (Oct 21, 2007)

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 .


----------



## CharlesNeil (Oct 21, 2007)

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 .


----------



## shampeon (Jun 3, 2012)

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


----------



## Redoak49 (Dec 15, 2012)

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


----------



## CharlesNeil (Oct 21, 2007)

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


----------



## BinghamtonEd (Nov 30, 2011)

Wow, certainly not where I saw this thread going…

Charles, since we have your attention here, can you weigh in on the sterrated vs non-sterrated sandpaper when using WB finishes? I had no issues with the 3M Pro-Grade, wiped down with the 1:1 mixture, under Target finishes. Based on your experience … Did I get lucky? Does that paper have a low enough sterrate level? Or, does it really not matter as much as everyone makes it out to?


----------



## CharlesNeil (Oct 21, 2007)

in my opinion its one of those "key board " expert opinions that caught on, Crystal-lac still says to use silicon carbide and to avoid the sterated papers, I have used and have a ton of folks who use the sterated paper everyday with no issues. I would guess that if someone bought some really inferior sandpaper it could be an issue , possibly ,but again no issues here , ever. We use sandpaper from Industrial Abrasives , called Rhyno Pads, they are excellent for mid coat sanding . http://www.industrialabrasives.com/blocks-and-pads-rhynosoft-pads-c-80_307.html our go to for midcoat sanding is 320 , if using a thin oil finish then 600 or 1200 .

I am pretty confident that sandpaper is not the OP's issue. Then again im not sure of a sandpaper that has a rubberized non slip backing .


----------



## BinghamtonEd (Nov 30, 2011)

Thanks for your response, Charles. I may have to pick up some of those pads, the pricing is not too bad. It's nice to know that it's a bit over-hyped, I'll just steer clear of low-quality papers/blocks and stick to what's been working.

I didn't buy the sandpaper because of the rubberized backing, and I haven't found it to be of much benefit for what I use it for. But, I guess if you had made a custom sanding block for some unique sanding task, it might help, the backing is pretty non-slip.


----------



## CharlesNeil (Oct 21, 2007)

I have never heard of or seen it , sounds interesting .


----------



## 000 (Dec 9, 2015)

Was there ever an answer to the original question? 
Maybe ego's got in the way and derailed the thread?


----------



## Cricket (Jan 15, 2014)

C'mon y'all. Let's stop this bickering.

IMPORTANT: Respect For Others
http://lumberjocks.com/CricketWalker/blog/42535


----------



## ThomasChippendale (Nov 6, 2015)

Back to the topic, I had the exact same thin happen to me last time I sprayed waterborne poly on mahogany doors, fish-eyes abounded. The doors were primed and had already 3 coats of poly applied by brush and no fish eye were present. I blamed the gun and or compressor for contamination and since I ran through the can of finish, got a newer and fresher can from the store. The later reduced the amount but there were still some. I finished with a brush and got a decent finish but not the thick, clear gloss no brush mark you get with a gun. I believe the compressor was the source of the problem, oil or silicon leaching into the finish probably.

BTW, presence of silicon is the first thing to look at for fisheye, then there could be other causes. My first can of finish was past due, the second was fresh and handled better. Look at the date on the cover next time you buy a can of finish.


----------

