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Comparison of Wet & Dry Thicknesses for STI Coatings

Written by STI Firestop | Apr 20, 2020

 Third-party tested and listed designs (e.g. UL Systems) specify wet and dry film thicknesses for applied coatings. Where dry film thickness is specified, it should supersede. Always follow the parameters of the tested and listed design for coating thickness specifications. 

Dry film thickness (DFT) is directly proportional to percentage of volume solids in the coating. 

The formula to calculate DFT based on wet film is Percent Volume Solids x Wet Thickness = DFT 

 

Series AS Solids Content by Volume = 66.5%
Wet Thickness, mm (in.) Dry Thickness, mm (in.)
3.2 (1/8) 2.1 (3/32)
3.1 (1/8) 2.1 (3/32)
3.0 (1/8) 2.0 (3/32)
2.9 (7/64) 1.9 (5/64)
2.8 (7/64) 1.9 (5/64)
2.7 (7/64) 1.8 (5/64)
2.6 (3/32) 1.7 (5/64)
2.5 (3/32) 1.7 (5/64)
2.4 (3/32) 1.6 (1/16)

 

Series SFS Solids Content by Volume = 70.1%
Wet Thickness, mm (in.) Dry Thickness, mm (in.)
3.2 (1/8) 2.2 (3/32)
3.1 (1/8) 2.2 (3/32)
3.0 (1/8) 2.1 (3/32)
2.9 (7/64) 2.0 (3/32)
2.8 (7/64) 2.0 (3/32)
2.7 (7/64) 1.9 (5/64)
2.6 (3/32) 1.8 (5/64)
2.5 (3/32) 1.8 (5/64)
2.4 (3/32) 1.7 (5/64)
2.3 (3/32) 1.6 (1/16)

 

Series FT Solids Content by Volume = 86.5%
Wet Thickness, mm (in.) Dry Thickness, mm (in.)
3.2 (1/8) 2.8 (7/64)
3.1 (1/8) 2.7 (7/64)
3.0 (1/8) 2.6 (7/64)
2.9 (7/64) 2.5 (3/32)
2.8 (7/64) 2.4 (3/32)
2.7 (7/64) 2.3 (5/64)
2.6 (7/64) 2.2 (5/64)
2.5 (3/32) 2.2 (5/64)
2.4 (3/32) 2.1 (5/64)
2.3 (5/64) 2.0 (5/64)
2.2 (5/64) 1.9 (5/64)
2.1 (5/64) 1.8 (5/64)
2.0 (5/64) 1.7 (5/64)
1.9 (5/64) 1.6 (1/16)

 

Notice: These values are approximate. Many variables can ultimately impact wet and dry thickness measurements. Volume solids content in coatings is a nominal value and may fluctuate slightly from batch to batch. Opening geometry, packing material type and density, temperature, and humidity may ultimately impact the drying or curing of the coating. This document is provided for informational purposes only.

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