I’ve been repairing a carbon-kevlar kayak. I had used alayer of West System 105 epoxy resin with 205 hardener but did not like all thebubbles that appear on adding the hardener and are v difficult to get rid of.After a cure period of more than a month I sanded to 80-grit and recoated witheasycomposites RapidRepair epoxy resin and fast hardener. When these are mixedthere are no bubbles – so preferable to the other brand!( I cleaned aftersanding with acetone but waited for that to dry before re-applying resin).Where I applied easycomposites resin on top of the West Systems resin, theeasycomposites resin did not harden fully and went slightly milky. I know I hadthe resin/hardener mix correct (100-33) because the mix hardened in the mixingcup and on parts of the kayak where there was no West System resin underneath.After waiting a couple of weeks for it to cure, I found it was still a bit stickyon the surface and although it had hardened it had the texture of polyethylenerather than a hard clear resin and could be peeled off with a paint scraperblade (luckily because it won’t sand off easily). So there was low adhesion tothe West Systems resin underlayer as well as the hardening issue. Has anyoneelse experienced this? 

one general rule with any RESINS and hardeners what you start with you carry on with !! never mix other brands with other brands !! not all manufactures use the same recipe's for there products that's why some are better for some things than others !!