What would be some signs to look for to know if some stuff aint purged enough? Would you get sick? Headaches? Dizzy? What are the effects of bad oil?
for the most part, it tastes like absolute shit, and is very very harsh. makes you cough and not be able to breathe. it might also taste like what it was made with (ISO, everclear, or bad butane if it was used). if it was made with shitty, moldy, or fertilizer filled weed, then your butane will be concentraded shit, mold, or fertilizer and become about as unhealthy as cigarettes. it also looks, and smells like black tar resin shit. also, it will have tiny bubbles in it, or big bubbles, and thousands of them if there is still butane. if you let it sit for a few days, does it form new bubbles on the outside layer like this?
if its a nice golden, shatter piece that is somewhat see through, then its good.
if it cracks and sizzles on the nail, it could be bad.
when thinned out, what color is it? if there is any green, or pure black, that is shitty/gross oil most of the time.
you want a nice golden, hard (not gooey for the most part) oil that is silent when smoked, and doesnt absolutely kill the lungs and make it so you cant breathe, which it probably will. unless its been winterized.
if its real real bad, and improperly made oil, then yes it can make you sick or give some people a wicked headache.
sometimes good oil does the same too though... got dizzy and sick (greened out I guess or something)