So if I am measuring my nic, flavors, and vg with a syringe, does the ml indicated account for what is in the needle to. I have several needles in 3ml 5ml 10ml and 20ml. I just want to know if my results with a syringe will be consistently the same accuracy.
As long as you're not drawing more air into the syringe so you can push out the remaining liquid on the needle, the amount of liquid the needle contains shouldn't matter, as it is left behind even after the syringe has been fully plunged.
Except that the tip of the plunger is rubber and it will compress when it reaches the bottom of the barrel. This will squeeze out nearly every drop, and the needle will "sneeze" air and droplets. It's totally empty, and the DIYer has now used 0.5 of a ml more than they meant to. This can be crucial if they are measuring 100mg nicotine, or a really strong flavor. I suppose if you were very gentle with it, you could stop as soon as it bottoms out and still have liquid in the needle, but that doesn't account for the void at the bottom.
The void at the bottom of my 10ml syringes holds about 0.2ml before I reach the "0" mark. If I have a 12 gauge needle on it, that's another 0.2ml. Maybe it's just the brand of syringes I use, but if I put 5ml in a syringe with a needle, and squirt it into a 5ml test tube, it always comes out to be over. I have used a few different test tubes to check. That's why I don't trust syringes to measure small amounts of anything, unless there is already some liquid in it.
In this case, the user isn't being consistent with how they are operating the plunger, pushing the plunger down further than they originally had it. As you surmised, it will throw off the measured amount. To be fully accurate with a syringe, one must compress it back to the original starting point, but no further.
Yes, the user must be very careful about how they use their syringes. I'm afraid not everyone is though. And this still doesn't account for the poor job of marking the increments, at least on the 10ml syringes I have tried.
The two brands I have tried take about 0.2ml before it reads "0ml". If the user starts their measurement from -0.2ml and not 0ml, there will always be a 0.2ml overage no matter how careful they are with the plunger. If they're making a 5ml test batch, and the ingredient they are measuring is 100mg nic, that's a pretty big screw up.
I've been pulling the plunger back to the ml mark I want and stopping, even if there isn't liquid up to that point, to take into account the air that's in the needle/tip when it starts. Mixed a couple in 7ml sample bottles from Five Pawns, and they came up to the exact spot that I originally received the bottles at, so I feel that (With my equipment anyway) everything is pretty accurate.
Hell, syringes don't even account for the void space at the tip, so they most defiantly don't account for the needle. When using syringes, you must not put your crucial ingredients in first (nicotine or strong flavor) because of the void at the tip that you must fill before you even get a measurement. By the time you fill it up to 1ml on your syringe, you most likely have about 1.2ml of liquid. So, if you are measuring nic or strong flavor with syringes, you should already have some VG or PG to fill the void so you can get an accurate measurement.
But, as /u/CloudAlchemist said, the amount of liquid in the tip of the syringe remains after dispensing what's in the barrel. Why would that throw off a measurement significantly?
Granted, it does mean a bit of waste though.
I stick by my statement.
There is nothing remaining in the syringe or needle if you use a good amount of force to extrude it. The tip of the plunger is rubber and will compresses when it reaches the end and will push nearly all of it. You may have a single drop remaining at the tip, but the needle and the void that I mentioned will be empty
If you are very methodical about it and stop as soon as the plunger makes contact, you may be left with a full needle, but this still does not account for the void at the bottom of the syringe (which will hold a good 6-8 drops).