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Thread: Slight orange peel with primer that I can't seem to solve..

  1. #1

    Slight orange peel with primer that I can't seem to solve..

    I purchased a 4 stage fuji system about 6 weeks ago and it has been a huge improvement. So much in fact that i actually enjoy finishing now instead of dreading the process I actually enjoy it.

    On this project I have been using target coatings emtech HSF5000 primer followed by em6500 pigmented lacquer as a top coat. I have no problem spraying the em6500 with a 1.8 or 1.5mm set with no thinning, i find that the 1.5 gives less over spray so i use that. The em6500 times around 45 seconds on a ford cup straight from the bucket.

    I have been having issues from the beginning with this primer. I can not seem to get it to totally atomize and give a uniform spray. I would say that 75% of the pattern is good but the remaining 25% is made up of varying size droplets. Out of the bucket it runs about 55-60 seconds. I have done several experiments with thinning and trying 1.3, 1.5, 1.8 sets and thinning to a viscosity of 30 seconds. While i have found that there is improvement with thinning and a 1.8 I am still getting a slight orange peel pattern. Just to clarify this effect does level out quite a bit so the end result isn't nearly as bad as the pattern looks on a piece of paper but it does require a little extra sanding.

    At this point I can spray the top coat straight, with viscosity of 40-45 with a 1.5 and get great results but even when I thin the primer to 35-40 and use 1.8 it's still not quite right. Do I need to get a 2.0 set? Any thoughts,
    Andy Giddings, i know you have plenty of experience with a fuji
    Thanks

  2. #2
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    That seems like too large a N/N set for anything around 40 seconds #4 Ford cup. The Fuji has a pressurized cup, yes? I have an HVLP conversion gun with pressurized cup. Anything in the 45 second range sprays great with a 1.0 mm N/N at about 5 psi to the cup. With my gravity feed gun I would use a 1.4 mm N/N.

    At 55- 60 seconds straight from the can I would still use the 1.0 mm N/N and only go to a 1.3 mm if it didn't spray well. GF's HP Poly is 60 - 65 seconds and sprays great with a the 1.0 mm N/N. SW's Kem Aqua Plus is just a little higher at 70 seconds but definitely sprays better with a 1.3 mm N/N.

    Orange peel comes from putting down too thick a film. I would go with a smaller N/N and spray a thinner coat. If it's too hot or the RH is too low, and that's why you are having to spray such a thick coat to get it to flow out, then try adding retarder or extender, whatever Target calls theirs so that you can put down a thinner coat and it still has time to flow out.

    John

  3. #3
    Generally when I'm spraying primer I don't care what it looks like. You have to sand it smooth anyway. I agree it makes the sanding quicker if you have a nice smooth level finish, but you have to sand it anyway.

  4. #4
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    Evan, I'll second John's comments. I've only ever sprayed primer with a 1.3 max (in fact, for BIN shellac primer I use a 1.0). Try lighter coats, no thinning and 1.3 max needle. A four stage Fuji should have no problems spraying even thicker materials (mine was a 3 stage and could spray most materials without thinning). Also, primer should be sanded after each coat as indicated by Leo.

    The first coat is not going to cover very well (at least with BIN it doesn't) and I find a couple of thinner coats is better than trying to get complete coverage with one. Also, the smaller blemishes only show after the first coat so those have to be dealt with and primed again before moving to the top coat.

  5. #5
    Thanks guys, the one thing I haven't tried is the primer straight with the 1.3. Since I sand it all out it hasn't made a difference in the top coat. I'm just trying to figure out the fix mostly from a familiarity with the equipment and process than to fix an end result. The more comfortable I get with the system the less time I am having to spend testing flow, size and air adjustments on paper which has significantly improved my efficiency. This issue with the primer is more along this line rather than a problem with the finished product.

    After using only airless systems for years it is difficult for me to tell if my settings are ideal since anything is a vast improvement. Obviously I am using significantly less material and have far greater control over the airless. However after hearing your suggestions about smaller cap sizes I am wondering if dropping the needle size on the top coat might reduce over spray even more. When the manufacturer suggests using a certain cap set should I assume or consider that with a 4 stage turbine that I may want to use a smaller size than suggested?

    Thanks

  6. #6
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    Evan, regarding cap size recommendations, I found the General Finishes to be ok for the Fuji 3 stage I had - but the range of sizes recommended often covered two of the available sets. My approach was to use the larger one to start with and only change if I had a tricky finishing job to do (lots of verticals, tight corners etc). I think you'll find with the 4 stage you have more pressure available to you at the gun (9.5 vs 6 on the 3) which should mean getting good atomization with a smaller set. You'll know when you've gone too small as you end up with an almost dry finish like overspray, instead of an even wet finish. If you haven't already got one, I would recommend a wet film gauge as this really helps to take the guesswork out of the job.

    In terms of overspray, although its reduced with HVLP compared to airless, you're still around 65% transfer efficiency. There's a good article about how this can be calculated/measured and the factors that are relevant here http://pprc.org/index.php/2012/p2-ra...nt-operations/. Personally, I recognize that the amount of overspray I get now compared to when I started is a lot better due to practice, but still a long way from someone that does this for their job :-)

  7. #7
    Andy, i see what you mean. When i used the 1.3 with the top coat I was finding that I was getting less over spray but the edges of the fan where almost drying too fast not quite turning to powder but close. With the 1.8 I was turning the airflow down and fluid to keep the transfer rate manageable and reduce blow back. I think the 1.5 is probably the best choice.

    This is probably one of those situations where i am getting hung up on trying to get absolute perfection and efficiency which is really not crucial on a primer coat. I find myself obsessing sometimes about improving efficiency which is definitely a factor of my limited space. I think im probably maxed out until we move next year and i can build a new shop.

  8. #8
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    Evan, efficiency for a hobbyist is going to be mostly about technique which is going to require a lot of practice and the feedback from appearance/film thickness. For primer, as you state, appearance is not as important but I can understand wanting to minimize waste.

    Personally I would not turn the airflow down unless I'm spraying into a tight corner or the inside of a cabinet and don't want the spray blowing back. A good way of avoiding this is leaving the back off the cabinet but sometimes that's not possible. I tend to adjust the fan pattern/fluid delivery depending on whether I'm spraying a face or edge/vertical or horizontal, but leave the flow alone. For fluid delivery my starting point on the Fuji is two complete turns back from fully closed if that helps. When I do an edge I close the fluid delivery down by one turn and close the fan down depending on the size of the edge.

  9. #9
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    As a hobbiest I never worry about transfer efficiency. I spend my energy focused on getting the best looking finish I can. I never change the fan width or flow knob after I have a good pattern. If it takes a couple of extra ounces of finish because of my wasteful habits I'm OK with that. I soon forget that it cost an extra $5 in finish; seems trivial to me after spending hundreds of $'s on wood and hardware and investing scores of hours building something. And much better than having a defect looking at me every day.

    John

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