ORIGINAL: Columbus Ron
I was in Home Depot today and I saw a tube of Bondo Polyester Resin Hardener. It is a liquid not a paste like the red or blue hardeners used with glazing putty or body filler. This hardener is designed to be used with the Bondo Polyester Fiberglass resin.
All glazing putties and body fillers that I'm aware of are polyester based.
Are all polyester resin hardeners interchangable?
In otherwords, can I use the liquid Bondo Polyester Resin Hardener in place of the red or blue paste type hardeners.
The reason I ask is that I only use very small amounts of glazing putty and estimating how much paste type hardener is rather imprecise. The instructions on the bondo polyester resin hardener say to use 10 drops per 2 ounces of resin.
I can weight the resin then add the appropriate amount of hardener.
Thanks
Ron,
The hardeners available at the home repair centers are typically MEKP types. The "P" means "peroxide". The red or blue hardeners contain some amount of this organic peroxide which cures the resin.
I've tested a couple different types of organic peroxides over the yearsand they all worked in curing polyester resins. As to amount, it depends on how quickly you want things to cure. Too little and the resin will take forever it seems; too much and your pot life is only a few minutes. Bondo type of resin/filler OR standard polyester resin can be cured by the sun too (high concentration of UV initiates and carries out the cure, particularly if you mixed too little hardener)
But for me, the better filler is Poly-Fil, an epoxy based 2 part, full scale aircraft filler. The stuff comes in small tubs and is mixed 2:1. Sands and feathers beautifully after a 4 hour cure. Or if you have a heat source of 90-100 degrees, it takes an hour or so. This filler is considerably stronger than Bondo too. The tubs were a gift 20 years ago from a good friend and I'm just about ready for replacements. Aircraft Spruce carries it; or look up Poly-fil on-line