Roundup "" Weed & Grass Killer "spray clogging" Questions

...to use it for several weeks, a film/slim forms in the applicator bottle that prevents the mix from spraying (clogs the spray nozzle). Any ideas or is this a known problem? take the spray head off

I have 2 sprayers one is the Roundup Professional Sprayer the other is the all in one sprayer from Roundup - neither of them are working - what am I to do? Um what do you mean by not working. spray ...