Thanks to George DiScala, 3M's Application Engineering Specialist for this week's tech tip
Do you find sometimes the body filler you have been using for years occasionally appears more difficult to sand and/or produces more pinholes than you would normally expect? The chances are you received the wrong hardener for that filler. Chemistries of body fillers are designed by manufacturers to fit certain types of hardeners.
While the active ingredient in modern day hardeners is Benzoyl Peroxide, the chemistry between hardeners will be different and have different effects on the mixed product. As the containers look similar, it is quite easy to mistakenly pick up the wrong hardener. So next time you experience issue as described, immediately contact your supplier.