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Thread: Had some issues spraying

  1. #1
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    Had some issues spraying

    Curious if anyone has ideas on what happened to some areas I was finishing last weekend. What was supposed to be a couple hours spraying doors and face frames turned into a weekend long ordeal. Poplar face frames, mdf inserts. I primed with HSF5000 primer, 2.0 tip in my 3m accuspray 20lbs of spray pressure. I ran over them with 220 before spraying with a hand block and wiped off the dust with blue scott towels. So I started spraying EM6500 with a 1.8 tip, same gun same settings, I did thin maybe 5% with water. I hung the panels from hangers in my booth and sprayed them vertically, as you can see from the photos there are areas where it just didnt seem to adhere, seems the finish kinda "slid" off. I dont get it, these panels were not exposed to any type of oil, grease, etc. I'm very fussy about handling them. Part of me thinks it has to do with how the gun was atomizing the product?? I ended up sanding the panels smooth and spraying them laying down flat. I did not thin this time and used all the same settings and processes. The EM6500 laid down really nice and flat so I'm very happy with the end result.
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  2. #2
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    Just guessing Jeff, but I'd say you were spraying too heavily for the thinned finish to hang on the vertically hung door and it sagged. Laying it down flat was the right move. I try to spray everything flat if at all possible as it is so much more forgiving.

    I'm surprised you could use the same gun settings for the finish thinned or straight out of the can. You are about on the limit for EM6500 White with a 2.0 mm N/N. TC says the viscosity is 28 - 30 seconds Zahns #4 cup. That's about 100 - 110 seconds #4 Ford cup, which is what I use, and that's pretty viscous for a gravity feed gun with a 2.0 mm N/N, even though TC says you can use a 1.8 - 2.0 mm N/N set. 20 psi air pressure seems way too low, too. I'd think you would need more like 30 psi to have a chance at good atomization. Did you spray some burst patterns to see what the pattern was before spraying?

    When I spray something I've never used before I start by measuring the viscosity regardless of what the manufacturer says it is. If I don't have a gun that can spray it w/o thinning then I thin it to fit the gun and N/N set that requires the least thinning. So after thinning I put it in the gun and shoot some burst patterns on paper or cardboard and adjust the fluid and pressure settings with the fan wide open to get the best pattern I can. If the pattern still is subpar, I thin it more. Once I get the pattern so it's acceptable then I know my chances of laying down a smooth coat of finish is pretty good, at least on horizontal stuff.

    I hope this helped some.

    John

  3. #3
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    What John said...I also prefer to spray flat. I do edges first and then the face.
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  4. #4
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    Quote Originally Posted by John TenEyck View Post
    Just guessing Jeff, but I'd say you were spraying too heavily for the thinned finish to hang on the vertically hung door and it sagged. Laying it down flat was the right move. I try to spray everything flat if at all possible as it is so much more forgiving.

    I'm surprised you could use the same gun settings for the finish thinned or straight out of the can. You are about on the limit for EM6500 White with a 2.0 mm N/N. TC says the viscosity is 28 - 30 seconds Zahns #4 cup. That's about 100 - 110 seconds #4 Ford cup, which is what I use, and that's pretty viscous for a gravity feed gun with a 2.0 mm N/N, even though TC says you can use a 1.8 - 2.0 mm N/N set. 20 psi air pressure seems way too low, too. I'd think you would need more like 30 psi to have a chance at good atomization. Did you spray some burst patterns to see what the pattern was before spraying?

    When I spray something I've never used before I start by measuring the viscosity regardless of what the manufacturer says it is. If I don't have a gun that can spray it w/o thinning then I thin it to fit the gun and N/N set that requires the least thinning. So after thinning I put it in the gun and shoot some burst patterns on paper or cardboard and adjust the fluid and pressure settings with the fan wide open to get the best pattern I can. If the pattern still is subpar, I thin it more. Once I get the pattern so it's acceptable then I know my chances of laying down a smooth coat of finish is pretty good, at least on horizontal stuff.

    I hope this helped some.

    John
    Thanks for the input. I did do a couple test patterns and was pleasantly surprised how well they came out. I should get really start using a viscous cup but I can usually get a good read on my product after pouring and a few tests. Just seems weird that it did this in a few areas with no rhyme or reason. I sprayed these initially with a horizontal fan and moved up and down on the panels with a steady motion. Lesson learned on trying to save time and spray them hanging.

    BTW is water the best choice for thinning the products I'm using?
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  5. #5
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    You just got too greedy, trying to cover too much. The more you thin something, the easier it is for it to sag. That's why I like airless for thicker stuff-no thinning needed.

    As much experience as I have spraying different things, I still spray on horizontal surfaces every chance I get.

  6. #6
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    As far as I know water is the thinner of choice for WB products. I sometimes use Extender alone or in addition to water, but only if I need more open time for the finish to flow out. Extender doesn't cut the viscosity as much as water but longer open time can lead to more sagging on vertical surfaces. Horizontal is the way to go if the project lends itself to it.

    A plastic Ford #4 viscosity cup costs like $6. I check every new gallon that I use. You'd be surprised how much some products change. Probably not enough that you could tell visually, but the cup don't lie. I keep a cheat sheet with my spray gun kit that lists every finish I've used, what the viscosity typically is, and what my standard gun setup is. I use those settings to set up the gun for my spray burst test and adjust as needed.

    John

  7. #7
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    With waterborne finishes, water is the reducer but extender can also fill all or part of that need as John indicates. However there's a limit to how much you can thin a waterborne product. The reason is that water is the carrier for the finish. When you add too much water, you're spreading out the molecules of the actual finish, so you can start to have coverage issues in addition to sagging/dripping/running, etc. So any time you can optimize the gun to shoot the finish with minimal alteration, that's the better choice. I try to only use a little extender for its inherent benefits and not do any other thinning. That's worked well with the 6008 gun with the PPS system for me.
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  8. #8
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    You can safely add at least 10% water to nearly any waterborne. I've added almost twice that amount a couple of times and not had any problems other than having to spray more coats to get the build I needed. However, I'm with Jim that matching the gun to the finish so you don't need to thin at all is the best option most times. Airless and pressure assisted guns give you a lot more flexibility in meeting that objective with waterbornes which tend to have higher viscosity than comparable solvent based products.

    FWIW, the purple HF gun sprays some WB finishes beautifully when thinned 5% or so. At $10 with a coupon it's a true bargain.

    Bonus points. You can turn any non-pressure feed gun into a pressure assisted fed one by adding a PPS H/O cup to it with a separate air regulator supplying 0 - 10 psi air to it or by hooking it up to a pressure pot. Tom or someone else above mentioned it in passing but it bears repeating.

    John

  9. #9
    spray guns that are pressure have lapped needle nozzle.

    Some guns will leak if fluid is pressurized amount will depending on the fluid viscosity and pressure.

  10. #10
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    Quote Originally Posted by John TenEyck View Post
    FWIW, the purple HF gun sprays some WB finishes beautifully when thinned 5% or so. At $10 with a coupon it's a true bargain.
    Of course, to add to the fun...they have more than one purple gun now.
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    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
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    Quote Originally Posted by Jim Becker View Post
    That's worked well with the 6008 gun with the PPS system for me.
    Jim, which gun are you using and can you elaborate on the PPS system? I'm using the 3m accuspray gun and the disposable cup setup right now and like you stated I hate to start making adjustments past its "comfort level". So can a person retro fit a different gun to the 3m disposable cup setup? Thanks as usual!!
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  12. #12
    they have adapters to put the 3M system on just about any spray gun. Ive run them on old suction feeds as well. The satas came with large stainless cups I never used just went straight to the 3M stuff.

  13. #13
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    Quote Originally Posted by Jeff Monson View Post
    Jim, which gun are you using and can you elaborate on the PPS system? I'm using the 3m accuspray gun and the disposable cup setup right now and like you stated I hate to start making adjustments past its "comfort level". So can a person retro fit a different gun to the 3m disposable cup setup? Thanks as usual!!
    I use the same gun as John...the 6008 HPLV from Homestead Finishing with the PPS cup system. For the benefit of folks ready that are not familiar with PPS, if you remember the Playtex baby bottles that had the collapsable insert, the PPS system uses similar with about 5 psi of pressure behind them. That provides pressure assist for moving fluid out of the cup and makes spraying almost "anything" a pleasure. I generally use the 1.3mm N/N for waterborne finishes, but have actually been successful with the 1.0mm N/N with some products. I've sprayed SW ProClassic which is like mud with no issues. Cleanup is a snap. The cup inserts are disposable, but honestly, I've used a total of three of them over the last two and a half years since I bought the gun. I just wash them out with hot water while cleaning my gun in the same. Were I buying today, I'd opt for the LVLP version which I didn't know about when I was buying.

    Yes, you can retrofit many guns to use the PPS system. You just need the correct adapter for the particular gun you want to work with.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #14
    Is there a gauge on the gun that tells you 5 PSI or you have an adjustment to match it to the material? Im curious on the number.

  15. #15
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    Quote Originally Posted by Jim Becker View Post
    I use the same gun as John...the 6008 HPLV from Homestead Finishing with the PPS cup system.
    Ok, I looked at that system on the Homestead site. You and John have me convinced on it. After a little reading it sounds very versatile as I know I have a full kitchen to do in tinted EM6500. If it excels at the higher viscosity then I'm on board.

    Question, do you find yourself messing with the pressure to the container? I see 5 to 10 psi is listed, just curious if its another setting to worry about?
    A bus station is where a bus stops. A train station is where a train stops. My desk is a work station.

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