Hi guys, I just wanted to give our Australian RA members a heads up that around 6 months ago Barnes have changed the formula of their 4PU polyurethane resin. I only this week started using a fresh batch that I bought late last year and was having some issues with it.
I then discovered that they are using a new formula and instead of the 1:1 by weight mix ratio in the past it now has a 10:9 mix ratio (which corresponds to 1:1 by volume! I was quite annoyed by this (both the fact that I wasn't made aware of the change before I bought it and that they changed what was already a great product). 10:9 is such a pain, and mixing by volume isn't really practical at very small quantities. So I emailed Barnes with a complaint.
I received an informative reply from Ross and he explained that the reason for the change is that the old product cost had suddenly risen by 250%
He also said that the new product was far superior when cured and gives an extra minute of working time. Plus many of the users are mixing larger quantities by volume so it suits them better.
Initial tests show that unlike the old 4PU the mix ratio is really critical (get it off by much and it never cures to a hard state but rather a flexible, rubbery state). It also seems to generally take longer to cure. I need to do some more test casts and get used to the 10:9 mix ratio...