Red Hardener Vs. Blue

[SFbullitt]

What is the diff?  Any?  I don't think there is....couldn't hurt to ask.  Wich one do you prefer and why.

[hemi-hampton]

Depends on what color your bondo is LEON

[Doc74]

Some brands use the red harder as the regular one, as with most fillers and blue for the hotter days. I've used blue hardener to slow down the curing process without altering the mixture. When the shop reaches temps up to 110 degrees you have about 40 seconds to mix the filler, apply and clean the tools which is not all that pleasant. The blue stuff gives me double that time and it's a world of difference.

Many fillers have white hardener which is basically the same as the red so depending on the brand the blue you have might be just regular hardener.

Have a little test, take the same amount of filler twice, add 2-4% of each hardener and see which does what.