How much lead and silica sand in speaker stands?

Sand / Silica dust is a breathing Hazzard ... use ⚠ caution ... generally the more the better ...

When I see how a simple audio question turns into a virtue signaling contest I fear for our future. I really do. 

There's two things you're trying to do here. One is add mass so the stand doesn't rock as easily. This improves dynamics and bass extension. The other is to damp the ringing of the metal. This reduces glare and harshness and improves detail.  

Packed sand will come in good contact with the metal and do a good job of damping. But its not that massive. Lead is more dense and great for adding mass but its larger and won't control the ringing as well. That's why guys combine them. Best of both worlds. 

Works even better with a little mineral oil mixed in. Use just enough to get the sand damp. Mineral oil eliminates dust and helps the sand pack better. You want it packed, not loose. Mix lead in at the same time. 

Sand mixed with mineral oil is used in my turntable rack. Both the top and bottom shelves are sand boxes. https://systems.audiogon.com/systems/8367 

This rack was built some 20+ years ago. There's lead shot on top of the phono stage. The environment is still here, and the cancer seems to be under control. Oh and I haven't electrocuted myself. Yet. 

We now return you to our regularly scheduled irrational fear-mongering.

Lead shot now is expensive. I looked at the OP's system and if he is using the stands in the the photo, he needs quite a bit and sand can leak, over time, especially if you move them around. Been there, done both. I have found that small pebbles or pea gravel works very well with no need for sand and much cheaper. Very solid, no ringing and won't be a lead, sand, mineral oil mess if they need to be emptied for moving or to sell.

What?!?!?! What are you looking at? Filled with pure lead, sure, you got a point. But then they would be so massive you need a forklift. So how ... wait, I know this is asking A LOT ... but how about some common sense? Two bags of sand, $4 a bag (if its even 2 bags needed) plus 5lbs lead shot per stand.

Like I said, what this world is coming to.....  

Oh and to answer the question directly- fill them all the way up. As much as you can pack in there.

So why go to trouble of getting lead & sand, when pebbles or pea gravel will work just as well? Plus, it is much easier to deal with if a move is needed. 

" Like I said, what this world is coming to.....  "
Imagine that, someone else's view that is not yours. Deal with it.