Using Pipettes and Syringes Correctly

[Gerald C Koch]

A bit of information which may be helpful.

Pipettes are made in two configurations. There are those that are designed to deliver a specified amount of liquid and those that are designed to hold a specified amount of liquid. The hold variety should always be rinsed to get any solution clinging inside them while you should never do this with the deliver variety. It will usually give the type on the pipette or the box.

Syringes are always made to deliver a certain volume. So if you are using a syringe to dilute HC-110 or Rodinal you should never rinse it and add the rinsings to the diluted developer. There is a certain amount of concentrate always trapped between the plunger and the neck. This can be important when using extreme dilutions such as 1:100 or higher.

 

[Pgeobc]

I doubt seriously that the difference between TD and TC (to contain) instruments is of much concern in photography, especially when one sticks to a standardized routine. If you were in a quantitative analysis lab doing wet chemistry, then it might matter.

 

[polyglot]

Oh, there can be a real difference. I have a 50mL TD syringe that fits about 1mL in the nozzle, so I generally don't use it. Likewise, there are some very long-nose pipettes; great for accurately delivering X amount to 10 different destinations but wasteful when you just want to measure out one finite quantity.

 

[bdial]

Does the viscosity of the liquid being measured matter for either of these types of pipettes or a syringe?
For example, HC110 syrup is quite viscous compared to something like Rodinal, and presumably would leave behind a greater volume in the tube.

 

[mts]

For small volume try using a discarded insulin syringe. Clip off the needle and you can measure fractions of a cc quite accurately.

 

[Kirk Keyes]

And remember - NO mouth pipetting!

Get yourself a rubber bulb for your pipettes.

 

[jp498]

I use 3ml disposable (1 piece plastic bulbed) graduated pipettes for a variety of purposes; to suck up, measure, and dispense small amounts of developer liquid concentrate (pmk and pyrocat-hd), cyanotype coating chemistry, etc.. I also use one to dispense a couple drops of photoflo for the last film rinse. Consistency is probably more important than accuracy. When I keep them, I reuse them for the same thing, and rinse them a couple times in water, filling and emptying them at least 3x. They are a very handy, neat, and inexpensive means of measuring and dispensing. I got a big bag of them on ebay. For much over 10-15ml, I use a dayquil cup which is graduated from 5ml to 30ml on the side.

 

[eclarke]

I deliver with a dropper and I weigh it..Evan Clarke

 

[Monito]

I doubt seriously that the difference between TD and TC (to contain) instruments is of much concern in photography, especially when one sticks to a standardized routine.

+1

Consistency is key.