The trick to the mirrors is just placing one. Do not try to make a grow room w/ mirrors. However you will see better results placing a cheap door miiror directly underneath the light on the floor. Mirrors do not make hot spots as they are perfectly smooth. never use a damaged mirror"that may make a hotspot depends". This will cause a 2nd shine of your high power light giving off more light. Light is absorbed yes, in mylar too. The trick is to mix both. If you have a mylar of white poly tent put a cheap door mirror or a peice of scrap beneath the light on the floor. Do not allow heat to beat on the mirror. The light shined don't make heat, its the source so no worry about heat absorbtion when ya light is air cooled. When using a mirror you have to have a direct hit of the light. Mirrors on the side aren't as good as mylar but mylar is not as good as a direct hit of light on a mirror. It's very cheap to get a door mirror & it will give you good results. When you provide a direct hit with high power it provides an excellent shine upwards hitting underneath.