Since they absorb moisture, which decreases their effectiveness, salt hydrates require costly and impractical encapsulation, with a semi-impermeable coating for improved performance. Paraffins are waxes. They are readily available, inexpensive, and melt at different temperatures relating to their carbon-chain length. Paraffin can be incorporated into drywall in two ways, by direct immersion and by adding permeated plastic pellets to the drywall mixture during the manufacturing process. Since drywall is a porous material, it can absorb melted paraffin when immersed in it.
Extra paraffin runs off, leaving no buildup of wax.
Immersion times vary depending on the amount of PCM uptake desired, however, they rarely exceed ten minutes. Drywall dipped in paraffin becomes water resistant. Immersion is the simplest, lowest cost method for making PCM drywall. To produce large quantities of PCM-immersed drywall, manufacturers would need to make major modifications to equipment and processes. Polyethylene pellets, saturated with melted paraffin, then mixed with wet gypsum and compressed in sheet form, also yield production quality drywall.