Using Too Much Paint

Question:

We have an automated spray painting line running the same mix of ware day in and day out. We currently spray a baking enamel with a hot airless spray gun. We have what we consider an accurate method for determining paint use. Based on the number of square feet per gallon painted, we have experienced an unfavorable increase in paint use of 20–25% for the past four summers. In our case, this could represent as much as 500 gallons of lost paint per month. We do not experience these variations in the winter. It does get extremely hot here during the summer. Furthermore, our rate of production also increases during the summer months. Do you have any idea why we are using so much more paint per square foot in the summer? Thanks in advance. P. B.

Answer:

A 20–25% variation in paint use from Summer to Winter based on the number of square feet painted per gallon of paint used is difficult to explain. However, if you are spraying at the same paint heater temperature setting during the Winter and Summer months, which are according to you extremely hot, as you do during the winter, you are getting too much paint atomization resulting in excessive paint over-spray. I suggest you reduce the paint heater temperature setting during the Summer months to where you are just atomizing the paint. It is also important to remember that paint use is dependant on the transfer efficiency (T.E.) of the process, which is expressed as the percentage of the paint sprayed which actually coats the product. And in your case, the T. E. is reduced during the hot Summer months. Furthermore, the more paint you spray when your production rate is high and your T. E. is low, the more you will waste.