Amount of paint needed

Thanks,

RD

Most automotive paints give an estimated square foot coverage on the technical data sheet for the particular paint. For example, the PPG OMNI MTK acrylic urethane that I use indicates about 500 sf per coat per gallon with NO LOSS. Assuming 50% loss during application, that equates to 250 sf per coat per gallon. Assuming three color coats, that yields about 80 sf per gallon or 20 sf per quart. Using this as an example, a 25 sf project would need a little more than a quart in the as-mixed, ready to spray condition. Say three pints total, which would allow some extra to account for unknown variables. But it is dependent on the equipment used, the actual paint product and the application. The loss during application using non-hvlp equipment can be as high as 75%. The claimed loss for hvlp equipment is no more than 35% (65% transfer efficiency). That may or may not be achieved. It also depends on the coverage of the paint product. A higher solids paint can cover better for the same coat thickness so two coats can possibly do the job of three. Furthermore, it depends on how heavy each coat is applied. The typical per coat thickness for MTK is about 1 mil. That can be more or less, depending on the individual applying the paint.

In the end, it is a matter of experience in how much to mix up for any particular job. I never like to run short during the last coat, so I tend to mix on the high side of my own estimate and the resulting waste of extra product is the price I have to pay to avoid running short towards the end. I try to keep a mental note of remaining mixed product after each coat such that if it looks like I might be short or even close to finish the last coat, I can mix up a little more during the dwell time between the second and third (last) coats. Paints are expensive so any effort to minimize the left over waste is important. I've never been able to get it real close except by luck, since I never really paint the same thing over and over. Each job is so different from the previous one and my work is so intermittent, that a different quantity estimate is needed each time. My original estimate usually results in either significant waste or the need to mix more between the second and third coats.

Rod

Thanks for the detailed information. I am a beginner and this will be my first time at painting using a spray gun so I will plan on the worst case and then add a little more to be safe. Can you give me a rule of thumb on how long to wait between primer coats and then how long to wait to paint and finally how long between the paint coats? Sorry for the long sentance and I am sure that since this is my first time I will be repainting this tractor again in the near future.

thanks again,

RD

You might want to try getting an old car hood from a junkyard and practice some painting on it before attacking your tractor parts. It'll give you a chance to get used to not only your spray equipment but also the products you will be using. You should expect some amount of frustration until you get the hang of it. It's not hard but does require a little practice to gain confidence. Using products that provide complete, written usage information (preparation, mixing, application) goes a long way in minimizing problems but is no substitute for actual practice.

Rod