The bonding can also be affected by the amount of sizing or starch that is in the fabric when purchased. For the best results do pre- wash and do not starch.
Also heat and bond is particular on the temp used when bonding. If when the backing is pulled off prior to bonding to the next fabric the heat and bond is not a milky color , the temp on your iron is too high. Then when bonding do not use the cotton setting, using a lower poly setting. Heat and bond is a bit differnent in that it will be absorbed into the fabric if too hot and for too long.
Note :Heat and bond stains most batiks... permenantly both the light and the heavy. Ask me how I know this ... ARGGG.