b'What Causes Them?In the simplest terms, a blister is a confined air pocket within the layers of a roof system. For example, blis-ters can occur between the base sheet and cap sheet of a polymer-modified bitumen roof system (see Photo 4). They also can occur between a va-por retarder and concrete deck and have been observed with single-ply membranes adhered directly to light-weightinsulatingconcrete.Blisters even can occur between an uncured adhesiveandsingle-plymembrane (see Photo 5).The physics of what occurs in-sideablisterisgenerallyrelated to the Ideal Gas Law. If you took high school chemistry, you may re-member the relationship between pressure, volume and temperature for a given amount of a gas. (To viewtheequationsIdiscuss,seePhoto 4: This plate blister was cut in a cross-section Theequations.) as part of a forensic investigation. Note the sealed air The Ideal Gas Law is a corner- space created between the plies of this hot-mopped stone of our physical world. For ourpolymer-modified bitumen roof system. Plate and purposes, we can assume if volumelinear blisters were prevalent throughout this system doesnt change and the amount ofand were traced to cold mopping temperatures.gas in the blister is the same, we are BREATHE EASY, heres our product listAVAILABILITY AND FORMATS BITUMAR INC. CANADIAN ASPHALT INC.(MONTREAL) (HAMILTON, ON)PRODUCTS BULK BURPAK BULK Barrel (keg)(50 lb bags) (100 lb)LOW ODOUR oxidized asphaltwith an odour inhibitor (suppressant) withoutany added PPA in the oxidation process. T2, T3, T4 T2, T3, T4 T2, T3, T4 T2, T3, T4Benets: Less polluting. The kettles andtankers stay cleaner. Mops last longer.Asphalt ZEROpolymerized asphalt with a viscosityequivalent to LOW ODOUR oxidized asphalt T2 T2, T3 NA NAat a lesser temperature.Benets: savings on propane, less smoke,no odour and improved adhesion.SEBS LOW ODOUR Asphaltelastomeric asphalt with an odour inhibitor(suppressant) with a minimal elongation of 750%Benets: The ideal asphalt for the laying of NA SEBS 750 NA NAelastomeric membranes and fleece backmembranes as TPO, PVC and EPDM or for aphenomenal adhesion of surface gravel. It can replace urethane and glues at a lesser cost.NB: the bulk is available FOB factory (Montreal and Hamilton) or delivered in the greater Montreal or in the greater Toronto area.BITUMAR INC.|CANADIAN ASPHALT INC.11155 St-Catherine Street East, Montreal-East, QCH1B 0A4Tel. : 514 645-4561|bitumar.comORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 3 202415'