The engine turned over and backfired, black smoke frothing out of the tail pipe.
Indeed, this local cooling aggravates the frothing.
And Marsh's test is very unmanageable with organic liquids on account of the uncontrollable frothing that takes place.
A stainless frothing cup helps you make the perfect cappuccino, and a stainless steel housing provides easy clean up.
Cast iron stills are provided with a hemispherical head or dome, generally attached to the body of the still by bolts, and of sufficient size to allow for any frothing.