Water-based polyurethane - Spider cracks on edges?

[Chris Rich]

Hi there,

So, I've been spraying General Finishes Enduro on my cabinet doors. I noticed that after drying, a bunch of 1/8" spider cracks are occurring on the edges of some of the pieces. I say some because there are a bunch that seem to be fine. I'm using some of their extender in the mix and I had been using denatured alcohol to wipe of the dust after sanding. I'm spraying indoors at about 72 degrees and about 10% humidity. I would assume contamination but I'm not 100% sure yet. Does anyone have an idea what would be causing that?

Thanks, Chris

[John TenEyck]

Which Enduro product are you referring to? I had the same thing happen with Enduro Clear Poly recently, but I concluded it was because I had some 40 F air coming back through my exhaust hose onto the freshly sprayed piece. I would not wipe your work with DNA. I would sand, vacuum, wipe with a micro fiber cloth and then blow off with compressed air. I've never used the extender but that should be helping not hurting. You are mixing it thoroughly, yes?

John

[Chris Rich]

Hi John,

It's the black pigmented poly. I'm going to try without the extender and without the DNA. I am mixing thoroughly. I thought of one thing. Could it be that I'm not laying enough finish down which might explain the cracking on the edges. Maybe drying too quickly? I did notice that one of the pieces that seemed to have more finish didn't have the problem.

Thanks, Chris

[John TenEyck]

I've never used the pigmented poly. It's viscosity is higher than the clear, IIRC. Not enough finish? Hmm, don't know. I would think the cracks would be more likely with too much rather than too little finish, but that's just a guess. I think you'd have to shoot a couple of scraps to test out that hypothesis.

John

[Chris Rich]

In the meantime, I've emailed General Finishes to ask them their opinion. I notice that the drawer fronts that are finished only on one side turn out beautifully. But, the doors that I've flipping over seem to have an issue. I'm painting the inside of the door first then flipping it on nails and painting the good side. I've got one door where the spider cracks cover a whole area and not just the edge. It looks like a tiny jigsaw puzzle. I'm kind of at a loss....

307493

[Brian W Smith]

What spraying equipment and,have you noticed a time pattern to the problem......IE,early or late in the spray window?

Good luck,I know it can be frustrating sometimes,but you'll figure it out.

[Tim Platt]

I've sprayed gallons of the black pigmented poly (actually spraying white pigmented yesterday and today) without any issues.

And let me say I am not exactly picky about how I spray. I use a cheap $50 HVLP sprayer.

One of the reasons I like GF is it is VERY forgiving for hacks like me.

I have never seen anything even closely resembling what you have there. I would strongly suspect it is the alcohol, but I would also inquire as to what you are spraying it with?

If you are using a compressor is it possible there is some contamination in the line?

Tim

[Chris Rich]

I'm using a wagner conversion gun. I suppose it could be contamination. I'll try picking up an inline filter. One thing i forgot to mention is that in between coats, I am actually wet sanding instead of using dry. Could that be an issue? I'll try doing it with dry sand paper. The item I have pictured, I did not use DNA on it. It already had a coat of poly so I just anded it. I'm sorry for all the confusion. This is my first foray into spraying....

[Tim Platt]

The way I usually do it is I spray on the hour.. eg 10am. At 1045 I sand lightly with 320 frecut on a sanding block, blow off with compressed air and tack rag. That puts me at about 1 hour to recoat.

I never wet sanded poly.. not to say you can't do it. What grit are you sanding with? Maybe the subsequent coats can't get a grip because its too slick? I also never used the extender.. But the crosslinker would help the coats bond.

I have wet sanded the GF lacquer with great success (piano black finish).

Please let us know what GF says.. Good info to file away in the back of my head.

Tim

[Chris Rich]

Thanks Tim. I'm using 400 grit wet paper. So, maybe your suggestion is correct. I'll try the fre-cut dry 320 as suggested. In the meantime, I'll let you know what GF says tomorrow (or whenever they get back to me).

[John TenEyck]

Your picture is exactly what mine looked like when I had the problem with Clear Poly. I attributed it to low temps but I could have been, quite obviously, wrong. I thought it might be contamination, too, and changed the in-line filter on my gun. I never went back to try and prove it with the old filter, so that might have been it. Like another poster, I never wet sand and I try to stick to a regimen. I generally let a coat dry for 60 - 90 minutes, dry sand, vacuum, wipe with a microfiber cloth, spray off with compressed air, and apply the next coat in about 2 hours. If I'm forced to wait overnight, I will make sure to create some visible abrasions in the underlying coating before I spray the next coat by either using a coarser sandpaper or sanding a little harder.

John

[scott vroom]

Chris, I spray a lot of pigmented Enduro and have never seen that problem on that scale. The only time I've seen any surface cracking was when I touched up a small area and hit it with the heat gun because I was in a hurry....the hot air caused the finish to skin over too quickly and it quickly developed cracks.

I've sprayed very thin coats without a problem. I dry sand with 320 between coats and never apply any liquid when removing the dust. As was mentioned above, Enduro poly is very easy to spray and quite forgiving.

Rather than email, I call GF directly in Troy Wisconsin....they're easy to reach and very helpful over the phone. My suggestion is to call 800 783-6050 and ask for either Ryan or Chris....they're chemists and would be in the best position to offer expert advice. Good luck....and please post a follow up if you get it figured out.

[Chris Rich]

Hmm..so far, the response I got was less than helpful...

Not sure. Try adding about 5% Flotrol which you can get at Home Depot. It could be that in the dry climate the product is flashing off too fast. The Flotrol will help slow it down a bit.


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[Chris Rich]

Ok, so I called them and he says the little lines on the edge are probably "crows feet" caused by the product flashing off too quickly ( I am in the desert so 5% humidity). He also said not to use Floetrol but try adding Extender at 10%. I had been adding 5% or none at all. I think if I thin that much, I may have to change my nozzle. I'm currently using a #4 (1.8mm). I wonder if I need to drop it down to a 1.3mm or a .8mm

[scott vroom]

Hmm..so far, the response I got was less than helpful...

Not sure. Try adding about 5% Flotrol which you can get at Home Depot. It could be that in the dry climate the product is flashing off too fast. The Flotrol will help slow it down a bit.


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Flotrol is a common additive to slow the cure time. Why don't you give it a try? 10% RH is extraordinarily low and it's plausible that the moisture is being sucked too quickly from the wet finish. How is that less than helpful?

Where are you located where the RH is 10% this time of year?

[Chris Rich]

The reason I said that is when I called them on the phone, they told me definitely not to use floetrol. I am in las vegas. It's about 45% humidity today only because we had rain last night but normally, it's down in the teens. I'll give the thinning a try at 10% using the extender along with the other suggestions. It's clear that some of my techniques were not exactly the norm so I'll try and do things a bit more consistent on my next pass.

[scott vroom]

"Hmm..so far, the response I got was less than helpful...

Not sure. Try adding about 5% Flotrol which you can get at Home Depot. It could be that in the dry climate the product is flashing off too fast. The Flotrol will help slow it down a bit"

"The reason I said that is when I called them on the phone, they told me definitely not to use floetrol. I am in las vegas. It's about 45% humidity today only because we had rain last night but normally, it's down in the teens. I'll give the thinning a try at 10% using the extender along with the other suggestions. It's clear that some of my techniques were not exactly the norm so I'll try and do things a bit more consistent on my next pass."



I'm confused. Are you saying that someone at GF emailed you with the floetrol suggestion? And then when you called GF on the phone the chemist said to use extender instead? I've never used either with GF, but yes I was reminded that they have their own brand extender.


If low humidity turns out to be the culprit then I suppose you could invest in an inexpensive humidifier for your shop when finishing.

[Chris Rich]

Yes, that is what happened. I think they would prefer us to use their extender and they said, chemically, it's different than floetrol. The whole thing is quite odd but the best I can do is try to follow all the suggestions and tighten up my procedures.

[scott vroom]

Chris, I checked the GF website and found this article embedded in their blog:

https://generalfinishes.com/blog/2013/07/enduro-extender-featured-family-handyman-magazine-julyaugust-2013-edition#.VOy0pbDF-cI

I think what's going on is that GF has developed in house an extender that, while somewhat different chemically, may have the same or similar performance as Floetrol with Enduro Poly. If it were me, to be on the safe side I'd go with their GF Extender if for no other reason than to avoid warranty issues down the road.

10% humidity is really, really low and I think it's reasonable to try the extender to see if it solves your cracking problem. Let us know how it turns out so that we can learn along with you.

[Chris Rich]

Thanks for the info... I'm just waiting for some 320 pre-cut sandpaper to get delivered and then I'll try this weekend and report the results. Again, I appreciate the help from everyone in this forum

[John TenEyck]

I noted that the GF article also said that "Floetrol is another great additive", which makes the comment by the one GF person not to use it confusing.

John

[scott vroom]

John, I'm thinking that GF is trying to make a market for it's own extender, and are pitching it as "chemically different" than Floetrol despite some evidence that the net effect of both additives is the same or similar. I don't blame them for that, but they should at least get their story straight between themselves :rolleyes:

[David Kuzdrall]

Uncured poly (and many) cured types are not resistant to DNA. This could be a contributing factor. Please note that there is a big difference between drying and curing.

[Chris Rich]

OK, so I've been experimenting. I emailed GF to ask them how many mils the finish should be because it wasn't in their tech document. They responded 2-3 mils. At 2-3 mils thinned 10%, I get spider veins. The finish is drying too quickly in my environment (72F @ 30%RH). I then noticed that the can actually says 3-5 mils so I tried at 5 mils and that seems to work much better. In terms of my spraying technique, I think I'm not quite doing it correctly. I haven't been doing a cross-hatch pattern and I think I should. I'm going to turn down the flow a bit and do a cross hatch.

[John TenEyck]

That's interesting. My shop conditions are not far from yours at about 65F and 30-35% RH. The time I had spider veins with Clear Poly I probably had a pretty thin coat, too. I'm not so sure that spraying a cross hatch pattern is a good idea. It seems to me you want to spray a single, wet coat to get your 3 - 5 mils, so that the film can flow out. Spraying a cross hatch pattern means you are spraying two thinner coats, and the first coat is going to start drying before you get the second one on top. But I'm wrong a lot, so good luck and let us know how it works out.

John

[Chris Rich]

Thanks John,

I tried doing a crosshatch and it seems that the results were much better. I just turned down the volume a bit. The reason I wanted to try the crosshatch was that when I did a full pass at 5 mils, I notice that when it started to dry, I notice a faint white shadow line where some parts were curing faster than other but I do agree that it looks like it flows better. Probably my technique but something I noticed. For any one that's interested, my setup is as follows:

Wagner Conversion Gun
GF Enduro Pigmented Poly thinned with 10% GF extender
About 10psi at the trigger and 25 psi at the gun
#4 tip (I tried a number 3 and my gun couldn't do it)

You're results and setup may vary :)

Thanks again for everyone's help!

[David Kuzdrall]

How large is the piece you are spraying? Just curious with the size vs crosshatch technique.

[Chris Rich]

These are 21 cabinet doors so varying sizes but generally small...

[Chris Rich]

Actually, it turns out that the white "ghost lines" seem to wipe off with water and a soft cloth. Some kind of reaction during drying I guess. So, I'll go back to single pass which does seem to flow better...

[John Sanford]

One thing to keep in mind is that your wood is also at a very low moisture content. Between it sucking some moisture out of the finish and the flash off the outer surface, you're simply losing too much moisture too quickly. As an experiment, try wiping down a scrap piece with a damp cloth (lint free of course) just before shooting it. If that does the trick, then you could experiment with shooting distilled water (no mineral spots) for moisture (quicker), then shooting the poly. It could be worse though. You could be finishing outside during June. (I did a fair amount of brushing lacquer when I was living in Vegas....)

[Chris Rich]

Good advice! Can I do this if I'm doing subsequent coats of poly?

[Chris Rich]

So, I've been experimenting. If I try to shoot 5 mils in one direction, I tend to get bubbles. So, I turned down the material knob and shooting crosshatch to achieve 5 mils and finish turns out nice. Again, if I shoot for 3 mils, I get spider veins. GF suggested bumping the extender up to 20% but I think that's a bit much to I'll stick to cross-hatch. Thought someone would be interested in my experience....