In an ideal world it would be Butyl Mastic, but these days the "tradies" take shortcuts and use silly-con. Easy way to tell is to get a thin nail or strong needle and pierce the skin, by pushing it into the blob a few millimeters . If it comes out wet or tacky chances are its Butyl Mastic if it comes out dry its most likely silicone.
__________________
Steve, Di & Ziggy We named our Motorhome "Roadworx" because on the road works "On The Road Again" Ford Transit with 302 Windsor V8 conversion, C4 Auto, 9 Inch Ford Diff All Lighting L.E.D., 260 Amp/h AGM, 530 Watt Solar + Kipor Backup Gen.
Hi
As we all no
Butyl mastic generally black grey soft putty when new mild tack . Goes hard over time and looses colour . Losses its sealing ability
Silicon sets sold and rubbery /flexiable VERY VERY hard to remove items when this has been used .
Urethane sets hard and permanent
There are now RV silicon sealant . WAY WAY more flexible than std stuff and does not stick like superman --removable
Other outstanding Sika products are Sikaflex 227 and Sikaflex 255 extra.
Both are polyurethane specialist Automotive sealant/adhesives and are available in black, white and grey. They are UV stabilised, meaning they wont break down or lose elasticity in direct sun.
