ALCOA Aluminum Sealant....it comes in a tube...is "HAZ-MAT", so no one will ship it to you unless you buy a CASE of it. Even, then, they'd have to have a Haz-Mat licence to ship it. No one will touch it otherwise. If a dealer has it, you'll have to drive there to pick it up. I drove 160 miles round trip to buy mine---needless-to-say, I bought 4 tubes of it.
It is NOT the same as Vulchem. Vulchem works great indoors...but for a "wicking" sealant that fills the cracks, but disappears so you don't see a build-up where you don't want to (extra bulk)...this stuff is FANTABULOUS!!! Cost about $8. a 6 oz tube.. $1 an ounce...NOT bad... picking out the old brittle stuff is the hardest part of applying it. (maybe!...it's not easy to keep the 'steady-hand' to apply it either (read below)..)
I went to a dental office and found a dental-tech that had stainless steel 'picks' left over they didn't want; (they can't use them anymore---bcz they must use disposible ones for health department regulations)....IF they still have one or two laying around, they might GIVE them to you like they did me. Great tool for picking! Once the crack is empty of previous caulking...then you squeeze the liquid aluminum out of the tube SLOWLY and run the tube BACKWARDS with a very STEADY HAND...to allow it to 'run down into the crack'...you will continue to allow it to fill the cracks on the sides of windows/doors, etc. but you won't need to do it to the UNDER SIDE of them because the liquid aluminum won't 'run' UP. (of course!) ...that is where you'd want to use the Vulchem for a moisture/cold air barrier, bcz you can apply it with a gloved finger and push it UP into the crevace.
If you can't find this stuff... PM me...or email me....I'll dig it out (the tube) and get you the contact information. It's NOT WORTH SUBSTITUTING this stuff ... This is the REAL mcCOY...