Water bourne lacquer finishing techique help needed.

I'm in the process of finishing some walnut stair railings and posts, using ML Campbell's UltraStar Clear lacquer(USCl) (Satin).
I'm spraying with HVLP, (Turbinaire, 1500, 3 stage). 70F, 30%-40% Humidity.
I started with UltraStar sealer, sanded to 320, I now have 5 coats of USCl applied, sanding between coats, some at 220 some at 320.
My finish coat still has some blemishes in it, ( some small, very shallow depressions and some dust pimples).
Through research, the shallow depressions(cratering, fisheye) are possibly due to contamination or perhaps drying to fast.
I've added some MLC W-502-4 Water borne flow additive, which helped a little, but is still unsatisfactory.
My Questions:
If it is contamination causing the cratering, do I sand it smooth, re-seal and then re-do the final coat(s)? (I don't know how this happened or what may have caused it.)
Does anyone have experience in rubbing out this particular lacquer finish and can you explain the steps you used? (I've read Jeff Jewitt's site/articles, I'm hoping for some general experience with UltraStar/Water Bourne Lacquers).
Thanks for reading,
David.
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On Apr 10, 5:45 pm, "David" <cosmosatnointerbaunspamdotcom> wrote:>
David - it sounds like your fisheye problem is caused by contaminates in the finish, in the gun, or on the wood. Try your finish (from the same can and mixed the same way you spray) on a clean piece of wood and see if you get the fisheyes or craters. If so, you know it is gun or finish.
Try cleaning the gun well, and drying it out completely. Set the gun back up and test it again to see if it has cured the problem. Also, check out the filter on the turbine. If the filter is dirty, it can cause the turbine to really heat up and that will cause unpredictable results in your application.
If that doesn't clear it up, you know it is the wood. If it is the wood, try some MLC MagnaClaw after sanding, and that should do it. I believe, I am not sure, but you should be using Magnaclaw on tinted or colored MLC finshes anyway.
Once the culprit is found, you need to address the problems on your project. To make a long story short, yes, you have to sand them out. And unlike solvent based which I find to be more forgiving, you have to sand the craters out SMOOTH. Anything you leave behind will simply reflect itself out into the next coat where you will build it back with subsequent coats.
So get the gun problem fixed first. Try it out on a piece of plywood or a good sized board. Put the same amount of coats on your test piece as you do your finish. (Check into that Magnaclaw, too). Then once a 100% on sealer and applicator, sand out your work as needed and then recoat to proper thickness. I am not sure, but I think UltraStar is 3 mil. If you are going to sand a great deal to knock down the nibs, craters and fisheyes, you should plan on a final coat of about 6 mil, sand down as needed, then top coat that.

The process of "rubbing out" isn't one that is commonly used on balusters, railings and posts, even on upper end work. You are having problems with your application, caused by different factors. Trying to "rub out" the finish on balusters and detailed stairway parts would truly be a nightmare.
I think you should sand off what you have to smooth, then reapply. Your temps and humidity are just about perfect for spraying, so rule that out. If this is an unfinished house, (or finished for that matter), make sure you have about 12 hours for the dust to settle out of the air. Tape off your work area the day before. Mix your product, set up your gun, and do all that fiddly crap outside.
Walk in, spray, walk out.
As a sidebar, one thing that helped me was to extend my hose on my HVLP. I have a four stage, so I put another 6' of whip on the 25' hose and just that little bit has helped keep me from stirring dust as I don't have to move hose and machine so much.
For more information that you would think possible on MLC products and how to use them, go here:
http://www.woodweb.com/cgi-bin/forums/finishing.pl
It is not a friendly rodeo atmosphere forum like this one where you can post your odd questions at will. Every post is completely monitored, and Bob will throw you off if he thinks you are just some noob (right or wrong) looking for someone to tell you how to paint a doghouse. I would strongly suggest you search the archives before joining and posting.
Jewitt sells Target product, and I don't know if he is selling MLC now or not. But let me tell you, I would be astonished if you couldn't find all you need by searching the archives at WoodWeb. That's MLC country over there.
Robert
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wrote: [ snipped very informative and helpful response].

Indeed. Woodweb is full of good stuff. A genuine resource for pros and semi-pros alike. It's moderated, so never any trouble with global warming bushlshit either. (I hear they shoveling some warming stuff in Chicago today...)
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Thanks for all the great information.
I have re-cleaned my gun, tried some different airflow/product flow combo's but still had some problems. I cleaned the turbine filters, but heat build up didn't seem to be a problem, my spray time is only a couple of minutes.
I added a little more of the MLC flow additive, that helped a little.
One of the tips I gleaned from the woodweb site was a wipe down with ammonia between coats.
After sanding out the problems and a wipe with ammonia, the spray finish was almost blemish free.
I now am getting a number of tiny bubbles, some of which dissipate with drying. I'll add a little more of the MLC flow additive on my next test to see if that helps.
It looks like I'm going in the right direction now.
I know you suggested that rubbing out the finish was going to be a nightmare, I don't disagree, but, if I can't get the 'off the gun' finish blemish free, what options are there?
The desired finish/sheen is satin or a little less.
Thanks again,
David.
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David - I started a new topic. Look at the newer posts on the fourm for some more thoughts.
Robert
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On Thu, 12 Apr 2007 19:58:29 -0600, "David" <cosmosatnointerbaunspamdotcom> wrote:

My newsreader missed the original message.
I spray lots of ML Campbell waterborne lacquers with great success. I normally spray them directly from the can, via a Fuji 4-stage HVLP gun. With a suction feed cup or pressure pot, I use a #3 setup, with a gravity feed, I go up to a #4. I add nothing, no flow additive, water, nada.
As for the bubbles, you're not shaking the finish can, are you? Don't shake the can.
For what most folks consider a "satin" sheen, you probably want the dull product, not the satin. Satin Ultrastar is noticeably more glossy than most folks think of satin.
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