What's the difference between spectrum and spectrum sludge?

I plan to use it under my back seat and in my trunk. I already have some raamat and ensolite in my trunk. I did not do a good enough job on the trunk. Can I lay some spectrum on top of the ensolite or will this not make as much of a difference compared to bare metal. I plan to lay around 3-4mm. and ensolite on top.

Edited December 18, 200816 yr by keith89

spectrum has the consistency of thick paint while sludge has the consistency of peanut butter

I probably wouldn't put it on the ensolite, pull it up first

Thanks. I will have to see if I can remove the ensolite.