We have recently switched to Kester HM531 solder paste due to some extreme environmental conditions. It has worked well and allowed us to continue production where we would be down with our previous solder paste. We have seen a reduction in defects and an increase in stencil tact time. I really like this stuff. We have started however, seeing "foaming" at the wash. In talking to Kester, it seemed there was an inraction between some chemistries that we are using. We have since switched wave flux and are trying to specify a new rework flux. My question is, is there anybody using the HM531 Successfully and what supporting chemistries are you using?