re TAZ
Yes I think it's real. In fact I have no big experience, but I think that the high pressure requested to push or pull the oil is due to the bottle-neck represented by the needle. I have done a test of that. With a 21 needle I pull in the syrynge some olive oil, then I push out the air. So I put the needle in a glass of water and I try to aspirate. After a brief high pressure pulling, the water flow into the syrynge quite easily. So because only the oil in the needle (about 0.01ml) create the high-pressure of injection I SUPPOSE that a little rear-shift of the piston is sufficient to empty the needle and from here, if we are in a vein, it's quite easy(whit a normal pressure) pull into the syr. the blood.
This is only an "in vitro" test, I'm not completely sure of that.
In fact the problem could be another. When we self-insert the needle in our ass it's difficult to aspirate 'cause the syringe could slide a little between our fingers(oh shit!). Another important fact is that the needle could trepass or just touch a vein, damaging it.
In these cases, I don't know.
It is for this reason that basskiller suggest to move the pin(needle) in and out??? Is it a good technique?
As soon