> I tried merge last night, and it does the same thing as union.
> I think this may be because the objects are transparent..

Hughes is right. If you have nested unions, be sure to use merge only in
those who combine surfaces that overlap. For example:

union {
    // bottle
    merge {
        cylinder { .... }
        sphere { ... }
        cylinder { .... }
    }

    // black bottle head
    union {
        sphere { ... }
        cylinder { .... }
    }
}

This is a nested union. It allows the whole bottle (with head) to be moved
in one piece, but I put the merge only where it's needed. If this still
doesn't work, I guess it's because you've made the overlapping objects
hollow?  This will be another story.

Regards,
Hugo

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