Wednesday, January 8, 2014

The Whys and Hows of Expanding Foam

     The first thing to know about expanding foams is that there are two distinctly different species.  The first is a one-part that puts out a bead of foam and is applied straight out of the can, or a can mounted on a foam gun.  The second type consists of two cans (thus the name two-part foam) that mix in the hose joining the canisters to put out a spray of foam for larger areas.  Those two canisters can be as small as a can of shaving cream - or weight so much that they may be difficult to lift.  The larger variety usually sits on the floor, and the connecting hose has a nozzle on the end for dispensing the spray.

     Both one and two part foams are made from liquid polyurethane kept under pressure.  When the foam is emitted, it expands and creates a protective barrier that stops the passage of air, gases, water, dust, fibers, and sound.  It also keeps out insects and other unwanted pests.

   Some things make one-part foam a wiser choice than caulk in many situations:  First, the expanding factor - a can of our Purfil foam puts out tens of times more product than a can of caulk.  For instance, one 25 ounce can of one-part foam puts out 1200 feet of a 1/2" bead.  Our Handi-Foam two-part foam expands at an 8 to 1 ratio. Second, foam has a great R-value (insulating value) of 6 to 7 per inch.  Caulk has next to zero insulating value.

     Some things that make two-part foam a better choice than fiberglass in many situations.  Fiberglass can cause irritation to the skin.  It can also be inhaled when fibers break off and are carried through the air, increasing the risk of cancer.   Looking at the MSDS (material safety data sheet) on Purfil one-part, I see that, "None of the ingredients listed are classified by IARC, ACGIH, NTP, or OSHA as carcinogenic".  Unlike foam, fiberglass is susceptible to water damage, which renders it ineffective.   It can also harbor mold spores when water damaged, as many of us found out in the recent Colorado floods.  Then, of course, there is the insulating value as mentioned above.  The R-6.5 per inch for foam compares favorably to the R-3 per inch of fiberglass.  In addition, foams do not shrink or settle, unlike many other forms of insulation.  

     Although foam is easy to work with in that you can cut it, use a foam gun to exactly apply it, and use a cleaner if you make a mistake, it does take some practice to get used to.  Because it expands, it can blow out a door or window frame if the expansion properties aren't understood.  Foam cures with moisture, so it does not work the same in dry and humid climates.  Something else you will quickly discover if you get any foam on your hands, the foam will turn black and be rather difficult to remove. Make sure that you order the foam cleaner along with your foam.  It's a very good idea to wear a mask and gloves when you work with this product.  If possible, it is also advisable to keep the area ventilated until the foam cures.  

    You can see all of our one and two part foams on our website here:

By the way, we are running a manufacturers overstock special on Purfil 1G 24-ounce foam.  The regular cost for a case of 12 cans is $152.00.  While supplies last, the price will be $110.00/case.