After reading this thread I can see we have different results and of course,,,different opinions and theories.
One thing that always bothers me is when I read about a load running in 60/90 for a week to 10 days and finding grit at the bottom of the barrel.
So,,,we have to go back to the basics of tumbling which is rocks,grit,water and barrel RPM's.
Rocks is #1 so we'll start there.
If the correct amount of rocks and their sizes is not right,,,grit won't grind down all the way.
If too much grit is used it will not grind down all the way.
If too much water is used the grit won't grind down all the way.
If a barrel is turning too slow or too fast the grit won't grind down all the way!
Some of us refer to the above as a "recipe" and we do add different components to it such as soap,Borax,pellets,ceramic media,etc,etc,etc(depending on what type of rocks we are loading and what stage we are in) but the basic recipe is where we all start.
I think the most common problems I see in loading a barrel are too much water and not enough small rocks.
I do see over loading a barrel being the problem at times but not nearly as much as too much water and or not enough small rocks.
This brings me to question on how using used slurry can possibly help to grind down rough rocks?
If you consider that grit breaks down in 1/2 every 7-10 days in a rotary tumbler it(used slurry) has become 120/180 or even finer.Now add to this that you are not "refining" the used grit to separate it from the ground down rock so all you've really done is add a cushion of wet dust and fine grit to a rough load.All this wet dust and fine grit is actually a cushion and NOT needed or even wanted in a rough load!
Consider this,,,,,
You have a lot of rough boards you want to sand down so you start out with brand new rough sand paper.
After a while you run out of new rough sand paper so you go back and start using the old used rough sand paper to sand your boards.
Do these old used pieces of rough sand paper help you to sand down those rough boards faster?
?
Better yet,,,,use the old sand paper and throw down some saw dust from your previous sandings!
I don't think you'd do it with wood and used sand paper so why do it with rocks and used grit/slurry?
Something else we should consider here is that we nay be dealing with apples and peaches as far as barrel size and design goes.You can't compare a round barrel with a multi sided barrel or plastic barrel with a rubber barrel!
Each and every barrel design WILL give you different results so the "basic recipe' may have to be altered slightly in each case.
A round plastic barrel(5 gallon bucket,PVC pipe,etc,etc) has to rotate faster then a rubber multi sided barrel or the "tumbling" action will be too slow and the rocks will only slide back down the barrel and not "roll" over on top.
I can't find it right now but there IS a formula for tumbling barrel size.The length is directly proportional to it's diameter.
Tihs is where a LOT of home made tumblers have problems as there design isn't correct.
If we made a home made cement mixer out of (lets say) a piece of 24" diameter PVC pipe with no "blades" to carry the cement/rocks/water around the barrel would we mix cement at the same rate as a commercial mixer?
So,,,why would a round piece of plastic pipe tumble rocks as well as a multi sided rubber barreled tumbler?
I should say that I'm comparing the "blades" in the cement mixer to the multi sides of a tumbler barrel here.Sorry!
The blades carry the cement,,,the multi sides carry the rocks.
We ALL would love to speed up the rock tumbling process but there is only so much we can do to do that.
I have done more experimenting with this hobby then I would like to mention and can see no way that used slurry helps in the rough stage!
To me,,,the answer is in the basic recipe used for each tumbler and barrel design!
I've been "chastised" for opening my big mouth in the past so it won't hurt to get a tongue lashing again! ;D
connrock