Did a test of some compounds when I was at Hawaii convenience store
Skill used : Junior alchemy 7.08
Items used : Fine crystal + Fine grass * 12
Results
Blue Crest x 5 (-8)
Purple Crest x 2 (-9)
Yellow Ring x 4 (+2)
Crystal Cuff x 1 (+1)
Hope that helps someone out there
Precis from Virgo ^^