When we process Elderberries, we don't use the steamer. What works
better for us is to cook them, with barely enough water to cover them, until
the skins burst. Then put them through a fine sieve which yields a clear
juice. Saves alot of cleanup time.
On the subject of 'clean up,' when we have a stubborn stain in a bottle
(or thermos), we add a handful of little stones, plus water, and shake until
clean.
I've found that the riper the elderberries the less goo that is
produced. Also, the last two years, I used a steam juicer to extract
the juice & that makes a tremendous difference in the amount of goo.
However, the steam juicer produces a much different wine than using
whole fruit in the primary, I've found it to have a lot less tannins.
~mIEKAL
Also if you want to use something organic for cleaning the glassware,
I've found that the citrus cleaners work quite well.