Bernard - I have one of those,

(having tracked it down eventually, then got lost getting back here). I have 2 inkpots and 2 globes of different sizes in this exact design. They really do not have these Nazeing-style bubbles. There is no outline of concentrated enamel around the bubbles. If I look through the base towards the light, I can see some bubbles have a "concentrated"
clear outline.
I'm as confused as ever.
I can see this style of bubble in Nazeing, in Grey-Stan, I've seen it in Ysart glass, I see it in that as yet unknown maker of stuff like this which is generally labelled "Scottish Glass". I really do not see it in any bit of Benny Motzfeldt at all.
I am wondering if we are talking about the same thing - but I have no examples of this sort of glass to photograph to show exactly what I mean by Nazeing style-bubbles! The concentrated colour is in a wide, flat "halo" around the bubble - and it is either round or slightly elongated round - and about 2-3 mm in radius from the bubble.
I do see a "particulate falling off the bubble", thin layer of colour on Marie's piece - but cannot see how it could be described as being the same as the wide flat halo.
I'll have to try to find something dyed to try your experiment. We don't use anything with extraneous chemical agents in it!