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mason Posted: Jul 28, 2015 01:34 PM	How soon can you spray over foam with another lift? This topic was emailed to me from SprayFoamMagazine.com staff, but some reason was not posted on my forum But here is the answer: It can vary depending on a lot of factors such as: ambient temperature, substrate temperature, thickness of pass, temperature of the liquid materials. The higher the temperature of the items listed above, the hotter the foam gets in the center. The thinner the lift the less time you can wait. For example a 2 inch thick pass may take 10-15 minutes to cool before you can safely install the next pass, whereas a inch pass may take only 5 minutes. Also the more lifts sprayed together, the longer it take for each subsequent lift to cool. Best way to tell is to follow this procedure: Spray 3 passes on a substrate similar to one that you are installing the foam at various thickness 1 inch, 2 inch and 3 inch. Using a digital thermometer measure the temperature of the foam in the middle of the foam. Check it after 5 minutes, 7 minutes, 10 minutes etc until it reaches it maximum temperature. If the internal temperature exceeds 200 degrees F, then it is sprayed too thick, cut back on the thickness until the maximum temperature is less than 200 degrees F. Keep measuring the foam until the temperature begins to dissipate. When the temperature begins to go down, it is safe to install another pass. Foam that is installed too soon after the initial lifts can have excessive exothermic heat that can causes, blowholes, fissures/cracks, low compressive strength, and low compressive strength. In very thick lifts, (10-12 inches or more), scorch and charring may occur and possible auto-ignition of the foam.

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mason

Posted: Jul 28, 2015 01:34 PM

How soon can you spray over foam with another lift?

This topic was emailed to me from SprayFoamMagazine.com staff, but some reason was not posted on my forum

But here is the answer:

It can vary depending on a lot of factors such as: ambient temperature, substrate temperature, thickness of pass, temperature of the liquid materials. The higher the temperature of the items listed above, the hotter the foam gets in the center.

The thinner the lift the less time you can wait. For example a 2 inch thick pass may take 10-15 minutes to cool before you can safely install the next pass, whereas a inch pass may take only 5 minutes. Also the more lifts sprayed together, the longer it take for each subsequent lift to cool.

Best way to tell is to follow this procedure:

Spray 3 passes on a substrate similar to one that you are installing the foam at various thickness 1 inch, 2 inch and 3 inch.
Using a digital thermometer measure the temperature of the foam in the middle of the foam. Check it after 5 minutes, 7 minutes, 10 minutes etc until it reaches it maximum temperature. If the internal temperature exceeds 200 degrees F, then it is sprayed too thick, cut back on the thickness until the maximum temperature is less than 200 degrees F.

Keep measuring the foam until the temperature begins to dissipate. When the temperature begins to go down, it is safe to install another pass.

Foam that is installed too soon after the initial lifts can have excessive exothermic heat that can causes, blowholes, fissures/cracks, low compressive strength, and low compressive strength. In very thick lifts, (10-12 inches or more), scorch and charring may occur and possible auto-ignition of the foam.

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