Size of a drop?

I assume you use a metering pulse pump to force the right amount out of the end at the right time. If this happens quickly enough and the drop formed is above the free fall size of the drop you can get repeatability. Too slow and the drop may fall before the pump has finished it's pressure pulse and a part drop will stay behind. Too fast and it will squirt off. Drop size is a function of viscosity, surface tension and tack or stringiness. Things like this need a lot of fiddling to get right, but once set up they should run fine as long as you keep the viscosity within a range. You will also need to cap the nozzle and clean it at the end of each shift and clean/test at start of next shift to avoid drying in the line and gumming up of the works.

Usually you work with the glue maker to set these specs for best operation.

If you use flow control and not a metering system it is a lot more susceptible to changes in viscosity changing the amount dispensed

I think that a drop is strictly a function of viscosity, but I'm not an expert on the subject at all.

surface tension, density, thixotropy, diameter of dropping aperture and the thickness and stuff the dropping aperture is made of also play a role.

This field is full of empirical solutions that the glue makers have determined by trial and error

that reminds me i do like a good drop

I only know that the drops would be different but I don't know what the relationship is (bigger for 1000 or smaller). It should be easy to perform an experiment. If you get a really sensitive weighscale, you could measure the weight of a drop at different viscosities. If the difference is too small you could measure the weight of, say, 10 drops for each viscosity.

I believe your question has to do with the amount of adhesive you're injecting, right? If your viscosity changes, the amount of adhesive injected also changes. But that's only true if the drop size is proportional to the viscosity (increases with the visicosity). If it were inversely proportional, it might not matter what the viscosity is since the amount would be self-adjusting.

I'm just saying things off the top of my head. I don't know if what I'm suggesting can be done since I don't know what your equipment looks like.

surface tension and density would be factors here, higher ST = larger drop. higher density = smaller drop.

get into thixotropy and gels and it gets comples. Glue makers often create jelled inks becsue they can make adjustments with meter pumps and have no fear the glue will drop off too soon if mehanically applied. If they actually want the drop to form to a precise size and then drop off just when they want it it needs good control and they will often have a striker to jar a drop loose in that case as that gives precise timing.