I am in the labeling machines industry and for tapered bottles/products it is mportant to have automatic machines.
Why? Because we have asynchronous motors regulated by frequency converters which allow us to set up the outlet speed of the label.
Another very important point is to ask your printing company to make the label regarding the tapered bottle's degree; this will allow to
apply the label perfectly on the tapered product and it will look straight as it should.
With the manufacture I work for, CDA, we do a lot of these machine for the wine industry, for the coating industry and sometimes for food
and we ask the product(s) samples in order to manufacture you the bottle/product pusher (that will hold the bottle while labeling) regarding
your tapered product.
Please let me know if you have any question or if you would like to see some videos.
Kind regards