materialssealing
The can of bitumen mastic says I can add up to ten percent solvent to make the mastic easier to apply. Applicable solvents list follows. The problem is the mastic is so stiff tat if I put a stick vertically into the mastic it doesn't fall – just stands still so it's unclear how I would mix the mastic with the solvent such that it mixes uniformly and the process takes reasonable amount of time.
What's the procedure for such dilution?
I like clear silicone caulk for this kind of job.
It will remain flexible after curing, so if the pipe gets bumped or moved around it won't break or crack like expanding foam. And the clear caulk won't stand out since it cures to a translucent light grey color which is similar to the siding.
There are aluminum to copper wire nuts available, like Ideals 30-16. Basically it is a wire nut filled with NOLOX. It is made mostly for mobile homes that have aluminum wire and updating devices that might have failed or if you want to change the color, etc... They are not cheap, about over a couple of dollars each. You can but them on the internet or at mobile home repair shops.
Never use wire nuts that are rated copper only. If you do you are looking at a failure in the connection for sure.
EDIT - For larger cable (I just saw mains in your question) you can used al/cu rated split bolts. Use plenty of NOLOX then wrap in rubber tape and then a good electricians tape, not the cheap black tape.
Do not use the copper split bolts, they are rated copper only. Make sure the connector shows al/cu ratings on it.
Best Answer
Leave the can in the sun on the next sunny day for several hours (if the ambient air temperature is warm). The sealer should be sufficiently softened to add the prescribed amount of solvent and stir with a sturdy mixing stick. (If the directions on either the solvent or the sealers label states otherwise always follow those instructions).