ISO and resin ratios off – field diagnostic tips?
Had a situation last week where I was getting soft, tacky foam mid-job. Eventually tracked it down to an ISO drum that was running low and had moisture contamination at the bottom.
Wanted to start a thread about field diagnostics for off-ratio foam since I see this come up a lot:
Signs your foam is off-ratio:
– Tacky/sticky surface = too much ISO or resin side issue
– Brittle, crumbly foam = too much resin (A-side rich)
– Off color (darker or lighter than normal) = ratio issue
– Unusual smell = contamination or ratio
– No cream time or immediate skinning = usually heat issue
Quick field tests:
1. Paper test strip – apply small bead, check tack at 30 seconds
2. Knife test – cut sample, check cell structure (should be uniform fine cells)
3. Measure mix ratio by weight per second from each side
Anyone have other field diagnostic tips they rely on?
Great thread. One more I use: the icepick test. Spray a golf-ball size bead and wait exactly 30 seconds. Poke it with an icepick or thin screwdriver. If it goes in smooth and the foam springs back = good ratio. If it tears instead of compresses = resin rich. If it goes in like butter with no resistance = ISO issue or heat problem. Takes 2 minutes and tells you everything before you commit to a full pass. I do this at the start of every job and after any drum change.