I know many people use some sort of reflective material while growing to aid lighting and I was curious about which materials are cheap and recommended. I am guessing regular aluminum foil doesn't cut it.
Big no to aluminum foil... I made that mistake... Cheapest you will probably find is either mylar online or go to wallmart and get a safety blanket (made of mylar).. So ya you need to use mylar, just do a search for mylar and it should answer any questions..
edit found this chart.. Mylar=90-97% reflective Flat White Paint=80-90% reflective Emergency Blankets=75-80% reflective Tinfoil=70-75% reflective Mirror= 60-70% reflective (it's just thin tinfoil behind glass, due to refraction in glass has lower reflective properties than just plain old tin foil) also note the tinfoil will cause hot spots and be bad for the plants.