This is something which has been bugging me for ages…
Toothpaste that has three different colours in it (like Macleans triple stripe or Colgate Triplemint)-
how do they make it so that all three colours always come out (and as stripes) at the same time when you squeeze, no matter how you squeeze the tube?
Inside the tube (I dissected one once) is just a single big, broad striped blob of toothpaste; the shoulders of the tube narrow in a funnel-like way so that when you squeeze the tube, the end of the big broad stripe is extruded through the funnel and comes out of the nozzle as a thin, long stripe.
like this
dissecting the tube was going to be my next step…
if that’s the case, how come if you squeeze it from a medial/lateral perspective as opposed a dorsal/ventral perspective, you still get stripes? wouldn’t you expect to get different proportions of the colours, seeing as toothpaste tubes are not perfect cylinders etc?
It is harder than you might expect to mix up the colours inside the tube, mainly due to their viscosity, but also because of the relatively small diameter and the absence of voids.
Wow, there wasn’t anything like that sort of complexity in the tube I cut open; no internal divisions at all and the nozzle was just a hole in the end (it was a three-coloured toothpaste).
I only buy single-coloured toothpaste so can’t do my own experiment, but it seems likely that there are at least two methods. I’ve seen plenty of explanations in “how does it work?”-style books that corroborate Cecil’s version and Mangetout has used his own empirical approach.
I remember using Signal when I was a kid that was basically white with red stripes painted along the sides (so that would have used Cecil’s method). Paste that is already striped inside the tube would come out with all the colours “embedded” within it. Maybe the OP could take a close look next time he brushes to see which method applies?
Wouldn’t the use of such a system as Cecil described bring the cost up significantly?
Cecil’s explanation applies only to Stripe toothpaste, a brand which I believe is no more. AquaFresh, the most popular striped toothpaste that I know of, comes in a tube with a clear plastic shoulder; one may plaunly see that the stripes run all the way through the paste, all the way down the tube.
