Soil mixture help....

So, I have decided maybe I'd try making my own bonsai soil instead of paying a lot for small amounts. Here is what and where I'm trying to grow (becuase I'm learning, that everyhing plays a part in being successful)...

I live in Pennsylvania (southwest portion), zone 6 but plants will be brought into cool basement during coldest parts of winter. I am growin some elms, maples, scheff's, dogwoods, and boxwoods. Maybe a juniper and redwood too... ;-)

I have been able to acquire the following items:

lava rock 1/4" size
pine bark fines 1/4" size
Napa oil-dry roughtly 1/8" size
Granite Poultry grit roughly 1/8" size

Using these materials, what would be my best ratios for success? I was thinking something like this:

30% Lava rock
30% Pine bark
20% Grit
20% Oil dry

Thoughts or suggestions? I have read probably a hundred articles on the differences/likes/pros/cons of oil dry/turface/pumice/akadema (or whatever it's called) and I know some of those may be better options, but ultimately, for availability and cost, this is what i have to work with. Any of your wisdom would be greatly appreciated!! THank you,
Jason

In simplistic terms('cause non-simplistic terms would fill a book), I believe the crux of the matter is to keep humidity up where the roots are, w/o keeping them wet. Do you want to water once/day, or is twice a day no problem? I use 50% pine bark fines to make sure once a day is enough.

That mix will work.
I would recommend sifting all of the components down to equal sizes, and combining them together for your soil mix after sifting. (Larger trees/pots get larger particle sizes, etc...)
Sifting out the dust from the mineral items and the really fine stuff from the Pine Bark, will keep the mix free draining and help to avoid clogging up the drainage screens on the bottom of your pots.

Check out this site for some pretty good info on soil.

I use Napa oil dri and some turkey grit when I have it on hand. Probably 90% oil dri 10% grit. If I had lava I would toss some in too. No pine bark for me. I water once a day with what I use.

yup... dat napa chit is da chit mang !!!

cheap and easy to access...

i use that with some pumice, grit and composted pine bark...

i dont really measure anything though... just eyeball it depending on the species...
less pine in ones that like it drier...

but i find that composted pine bark is a great safety net re: watering...

Just eyeball it also.