Glue Soak is the second upgrade for the Glue Gunner in Bloons TD 4, the first upgrade on the 1st path on Bloons TD 5, and the first upgrade on Path 1 in BTD6. When a Bloon is glued by Glue Gunner with this upgrade, the glue soaks through the bloon layers gluing all of its descendants. Without this upgrade, popping a glued bloon will make the glue disappear. In BTD4 or BTD5 Flash, gluing a Ceramic Bloon would be pointless without this upgrade, because Ceramic Bloons cannot be slowed down by glue in those games.
In BTD6, this upgrade will soak through all layers of bloon but will still never soak through layers of MOAB-class bloons. Furthermore, Glue Gunners are not even capable of gluing MOAB-class without Corrosive Glue or MOAB Glue.
Update History (Bloons TD Battles Mobile)Edit
Glue Soak price decreased ($200 → $150).