Seasonal and weather changes affect finish

Have you ever wondered why, despite following the same finishing procedures, one spray application comes out perfect…but the very next day the same procedure turns into a dogfight? Here’s a pro finishing tip: It could be the weather causing the problem.

You see, most coatings perform predictably within a certain temperature/humidity range, but if you move outside this range you can find yourself falling down the spray finishing rabbit hole of confusion. Even after years of professional finishing I can still get blind-sided by ambient conditions in my shop. So, I’m planning my adjustments for spring and summer weather conditions, which are coming up fast.

Here is my 3-pronged approach for mitigating in-shop climate swings, and I’d love to hear yours, too.

We obviously can’t adjust the outside weather, but we can adjust (1) our workshop climate, (2) the way we apply the coating, and (3) the coating itself.

Let’s take them one by one.  

  1. Adjust the Workshop Climate 

Ideally, this is where you’d start, because if you take care of this one, you don’t need to bother with #2 or #3.  

Make sure your finishing surface is clean.

If you have a lot of control over your work-space, adjusting it to the coating’s ideal climate range isn’t complicated. 

There are all sorts of portable heaters, coolers, humidifiers and de-humidifiers that can support (or stand in for) a HVAC system.  Also, keeping the surface you are finishing free of seasonal dust, pollen and other ambient pollutants is critical. A well prepared surface is a real problem solver.

Pro tip: The first 20-30 minutes after applying a coating is the most important because that’s when the coating levels, de-airs, and starts to shrink. 

If you can control your work-space climate during this critical window, it might be all you need to get great results. If 20-30 minutes still presents a challenge, move on to option #2 below.

  1. Adjust the Application Process

There are too many types of spray guns and apparatuses to give you any kind of reliable “rule of thumb,” but know this:

Pro tip: You can often mitigate weather/humidity swings by adjusting your atomization pressure, fluid pressure, and/or your tip set up or down one size.  Also, keep the wet film thickness of each coat within the specified range suggested by the coatings manufacturer. Too heavy of a wet coat in cold/humid conditions will take too long to dry – so keep those wet coats on the thin side of their spec. Likewise, in some cases a reduced heavy coat may be required in hot/dry conditions, so be prepared to adapt and modify.

Definitely consult your users’ manual and do some tests before you move on to your “live” work.

+1. Check your Air Supply

Yes – we all know, or should know, to keep our spray guns and fluid handling equipment clean and free of damage, but how many of us remember to drain the water out of our air compressor tank? When the dew point changes and humidity rises your compressor will be pulling in air that has a higher moisture content. Once the air is compressed the moisture, i.e. water, builds up inside of your air tank and will find its way into your outbound air line. To solve this problem I strongly recommend that you, 1) drain your tank on a regular schedule (purchase a automatic bleed valve that will do this for you…) and install and maintain a combination water desiccant and oil filter (if you have an oil-cooled compressor motor) that is positioned at the outbound air gauge, and also fitted to the handle of your spray gun right in front of the mini -regulator.  These two filters will make your troubleshooting procedure shorter and will ensure that you have a clean air supply.

  1. Adjust the Coating 

If #1 and #2 don’t work, you can also try reducing the viscosity of the coating you’re using.  

For example, if you’re in a particularly hot/dry climate, you can “thin” a water-based coating by adding basic tap water to it. 

Pro Tip: For our customers using EMTECH Series water-based finishes, I recommend using our SA5 Universal Retarder (start with 5% by liquid volume for spray applications; an additional 10%-20% for brushing/wiping).

These are just a few of the seasonal procedures you should take into consideration as your finishing schedule moves forward. Keep good maintenance records, observe your ambient environment and establish a good working relationship with your coatings supplier.

Have you had any “climate clashes” in your shop, and if so, how did you fix them? Please share your thoughts or see what others are saying in the comments section below.