Buds need to be close to the light and get as many PAR lumens possible. Focusing on different ranges for different times in the plants life.
A good strong Fertilizer Regime, with a balanced PH and Diet, i would suggest Organic ferts. Keeping your mediums PH in and run off EC in check is very important, as well as quality water.
definitely close to the lights promotes good growth as well as the intensity of the lights...more watts the better (that's why lumatek charges top dollar for "super lumens" on the switch) and as for the pH, the only thing that controls is the plants ability to take in nutrients...it promotes the healthiest growth...not necessarily dense. obviously to grow the best bud possible requires the healthiest plant possible. you are trying to create the factors that a plant is given when growing outside. the sun is the best thing for the plants, everything else we can recreate inside with very good results but artificial light truly is shitty comparatively to the sun.
onto the actual subject of the post the highest co2 you can get without harming the plant will make for dense buds as well as good air mixture in the room itself (lots of fans). what happens is this; the plant needs to breath just like you, only it breathes out of the stomata on the leaves. if the plant is not getting enough (or optimal) co2 the crowded buds grow more expanded in order to allow the airflow around the plant to increase so that it can breath better (just as if you were trying to breath under the bedcovers, it's hard so you move the covers to breath better, that plant expands to breath better).
the strain is just as important. you cannot change the genetics of a plant with nutrients you provide or the grow medium or light or air. you just can't, so don't try. some strains are just fluffy and stringy.
nutrients can boost growth and resin production but i've never seen any product claiming denser buds actually produce them. anytime you are looking for better results always adhere to scientific protocol for experimentation. keep a control, so when trying a new product, only try it on half of your plants so you have a side by side comparison through the plants life cycle to have a direct comparison. don't try to compare your previous harvest to a current or future harvest except for overall weight. i make sure to match strains as well. right now i'm trying soil amendments. so i have three plants each of eight strains. so i have three trays each with eight strains in them and each tray is identical except for the soil amendments. so when they all mature together, i will have eight plants of each of my three methods i'm trying, so i can have a real side by side comparison. anyways, if you feel that an additive product will produce denser buds, at least try the products out correctly to see the results.
in my experience, you will see the density increase from only two things. co2 and strain. everything else is just contributing to overall health of a plant which obviously the healthier the better!
HAPPY GROWING
