Do any of you use a viscosity flow device when thinner paint? I'm using summit urethane paint and the thinner i mix it the better it flows. Besides the risk of runs, is it okay to thin it more than the instructions say,? Thanks
If you're looking to maintain the viscosity you like, Zahn cups are not that expensive and if you ever need to touch up a metallic paint they make it much easier to match the panel you painted a couple years ago by keeping viscosity the same. Also, digital scales are handy for the same reason, add reducer by weight, not eyeballing the marks on the mixing bucket and hoping it's close.
In the olden days, if you were a regular customer, the supply house would give a viscosity cup, along with a flow chart.
Temp, altitude and humidity can play a factor but 99% of the time I follow directions. It's one of those "trust the science" things.
Mix per instructions. As said previously a little extra might be OK. Watch for shrinking, and die back. Generally air pressure and flow help with layout. If the paint is going on wet and you feel there is too much orange peal raise your pressure. To dry open the flow. Tip selection is important as well. Most high build primers available are being shot from a 1.8 or 2.0 tip. All guns are not made the same either. My 1.3 tip on the accuspray is OK for a door or smaller single panel, tough to run even wide open. But the 1.3 tip on my Sata will dump plenty of paint and if your not careful you will be cutting the car off the floor.
Yeah there's Zahn cups. I can't remember where it learned from but if you let the paint run off your stir stick it's supposed stream off and then form drops about an inch from the end of the stick. Maybe it's BS but I have done it and it did seem to work and pretty much fit the instructions.
We painted an off topic vehicle. A kitchen scale was used to determine the exact proportions using weight. Tare the container then add a volume of paint. For example if the ratio of paint to thinner is 2:1. Paint being 2 then thinner is 50%. We used grams as it is decimal units that are easier to calculate. (ie) If the paint is 500 grams then the weight of thinner would be 250 grams. It helps to have a calculator. Hardener is calculated the same as well. Have a container for each liquid and tare it or zero it each time with the container on the scale. Pour until the desired weight is reached. We tried using the viscosity cup but it was a pain.
I'm not a painter, so I always follow mixing directions as close as possible. I don't want to do anything to mess up a paint job by experimenting.
The best advice I got for using an HVLP gun was this. Open the fluid knob up all the way. Find the happy spot on the fan adjustment. Move as fast as ya can Overlap more
I would add to this, get closer ! Most people that haven't done this professionally. Are spaying way too far away from the surface with a hvlp gun. A closer distance to the surface. Translates to faster apply speeds and a finer surface finish. When I was taking my PPG certification class. If you were more than 4" away from the surface. They were on you to get closer ! and move faster ! They were adamant about it.
I just sprayed my Avitar Chrysler 300 overall this past fall. Amazingly I was able to rent a local body shops paint booth. It was warm in there, maybe 80 deg. But unlike spraying in the driveway where the sun heats up the metal too, it was uniform. The airflow across the car was fast and it sucked in dust from the through cracks in the walls and opening doors. I used large 3M style PPS cups with a HTE high transfer efficiency gun. If I was to do it over again I would use the largest cup size I could find. Painting cars in the 70’s with a Binks or Sharp gun, the cup size was always large enough to make it all the way around a big car with one fill up. With the PPS system, I was constantly running out of paint in the middle of a panel making it very challenging, and exhausting, to refill the cup and continue spraying. Because of this I had a few runs whereas when I am spraying something smaller I never get runs even though I lay on the paint to make it glassy smooth. Post up your progress, good luck!
I paint less frequently than I used to so I'm still using conventional sprayguns . I have noticed for quite a while that most of the new single stage urethanes and clearcoats are formulated for use in paint booths with a bake capability. These products are thicker (higher solids) and made to be applied (per tech sheet) with a small amount of texture/orange peel and the heat from the bake cycle "reflows" the material smoother and flatter. The bake also cures the product faster. When I spray new single stage urethanes and clearcoats, in a NON bake spray booth, I usually over reduce slightly or moderately, depending on the viscosity of the product. I also increase the spraying pressure (conventional spray gun) to atomize (watch your spray tip size) the product to a smaller droplet size and adjust my pass speed accordingly to minimize orange peel/texture. I will spray some test panels to check my wet out and see how the paint flows out smooth. I watch the temperature, humidity and airflow to see how it affects the "flash off" time between coats with each product I use. I also frequently use a small amount of urethane accelerator to speed the through cure of these new products when spraying without a bake cycle. If I over reduce a product I will usually add 1 more coat of product to the job (clear or single stage), to make sure I end up with recommended film thickness. It takes practice and experience to get the reducing of the product, the settings of the spray gun, the speed of your gun pass, and all the other factors "dialed in" to get the results you want. Early on I would make a checklist so I would be thorough when painting and remember all the variables and products I would need before starting to spray. I have 50 years of auto paint spraying experience with all types of paint, plus many hours of training from major paint manufacturers--and I'm still learning. Over the years I have seen many very talented painters, much better than I, but only a few with excellent technical product knowledge. I still find and read the TDS/tech info on all the products I use and others, for reference. I also have some very knowledgeable friends and colleagues I can call for support and expert advice--and of course, the HAMB is always a valuable resource. If you don't paint very often, be aware that with HVLP you need to have your lines, fittings and air supply/compressor all compatible for the high VOLUME of air in order for the HVLP spraygun to work properly. Sometimes it is NOT the best idea to just go the Harbor Freight and buy a HVLP gun. Here's some good information on purchasing a HVLP spray gun.
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