Help: EM6500 Mud Cracking

[Mike Romo]

Hey all,

I've been shooting pigmented EM6500 out of my Earlex 5500 HVLP onto a built-in bookshelf inside my home and am having some issues with mud cracking. Seems like I can't apply a full wet coat or I get mud cracking. The finish isn't running, but exhibits mud cracking, especially on some of the caulk lines (big stretch caulk has been cured about a month). I was also having this issue when shooting the shelves - full wet coats would mud crack, so I had to shoot it on a bit sparse in order to get proper drying.

Has anybody else had this issue? I contacted Jeff at Target and he had me brush out some samples, but none of those exhibited the same issues. I'm obviously applying too thick, but I'm having a really hard time walking that fine line between full coat coverage and 'too thick'

EDIT: I was using the 2.0mm needle that came with the gun and material was thinned 10% with distilled water

[Jim Becker]

That sounds like a pretty big orifice/needle for EM6500...and I've never had to thin the Target products, either. I don't know how my gun (Wagner HPLV Conversion Gun) translates to yours, but I run a number 2 needle and cap when spraying Target finishes. The only time I've had the issue you describe is when I lay it on too heavily.

[Mike Romo]

That's a good point, Jim. I guess we're on the same wavelength because I ordered a 1.5mm needle to see how that would atomize the product. The 2.0mm did okay, but the droplets were a bit large, so it left me wondering if it was my medicore gun or the needle. Unfortunately I've resorted to sanding back the cracks and brushing the last coat since I have to get this done ASAP, but I look forward to trying this when it arrives.

Out of curiosity, what size needle do you advise for EM6500? I used a 2.0mm because that's what Target has in their spec sheet.

[John TenEyck]

EM-6500 has a viscosity of 28 seconds Zahn #4. That's around 100 seconds #4 Ford cup, about the same as GF's Enduro White Poly. I use a 1.3 mm N/N to spray that product with my pressure assisted (5 psi) HVLP gun. I spray it with no dilution and it flows out beautifully and never mud cracks.

I think Jim is right. You need a smaller N/N.

John

[Wayne Lomman]

Mud cracking is generally over application as the others said. Cheers

[Mike Romo]

Thanks for the tips. I'll try my 1.5mm needle when it arrives and hopefully it breaks up the material better.

[Jim Becker]

It's important to remember that products like the EM6500 and it's clear cousin EM6000 are not "thick" paints and they generally can be sprayed beautifully with typical smaller needle sets just like many clears...and without thinning. A 2mm needle is more for "paint", rather than "designed for spray" acrylics like Target, GF, etc., offer.

[John TenEyck]

It's important to remember that products like the EM6500 and it's clear cousin EM6000 are not "thick" paints and they generally can be sprayed beautifully with typical smaller needle sets just like many clears...and without thinning. A 2mm needle is more for "paint", rather than "designed for spray" acrylics like Target, GF, etc., offer.

EM-6500 has a viscosity of about 100 seconds #4 Ford cup. Most WB clearcoats are less than 65 seconds, many less than 50 seconds. So EM-6500 isn't going to spray well with the same set up you would use for typical clearcoats; you are going to need a larger N/N or higher pressure if using pressure assist. I spray EnduroVar (45 second) with a 1.0 mm N/N, while Enduro White Poly (100 seconds) requires a 1.3 mm N/N. BM Advance (500 seconds) takes a 1.5 mm N/N. In all cases, I'm using 5 psi on the pressure feed side.

John

[Jim Becker]

John, is the EM6500 that much more viscous than the older PSL that came in white two generations back? That and the Fuhr tinted acrylic I sprayed for my original kitchen renovation cabinets all sprayed nearly identical to the clear.

[Marty Schlosser]

Hey, Mike,

As you noted from others' comments here, your needle size is far too large to effectively atomize that particular finish.

Experiment with your new 1.5mm set - without thinning the finish - and see how it comes out for you. Earlex systems aren't ideal for such finishes, but don't give up just yet.

That's a good point, Jim. I guess we're on the same wavelength because I ordered a 1.5mm needle to see how that would atomize the product. The 2.0mm did okay, but the droplets were a bit large, so it left me wondering if it was my medicore gun or the needle. Unfortunately I've resorted to sanding back the cracks and brushing the last coat since I have to get this done ASAP, but I look forward to trying this when it arrives.

Out of curiosity, what size needle do you advise for EM6500? I used a 2.0mm because that's what Target has in their spec sheet.

[John TenEyck]

Sorry, Jim, I have no clue what PSL is or was. TC's data sheet shows EM6500 to be 28 seconds #4 Zahn and that's about 100 seconds #4 Ford cup, which is 2X higher than EnduroVar.

John