Getting consistent reagent droplet size

Neemer

Gold Supporter
Oct 10, 2017
261
Fredericksburg, VA
I know you’re supposed to just allow the reagents to drop from the bottle without squeezing. However, I find that rarely happens and I’ve experimented with various methods to induce free-fall but haven’t found a method that works every time. Sometimes I turn the bottle upside down and it just smirks at me mockingly. Other times, the drops fall like a rain shower. Most often, I have to apply a steady light pressure to coax the drops out.

This morning I ran three samples for FC and got results of 7, 4, and 5. Results like these really irritate my OCD. Is there a trick I’m missing?
 

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
2,990
Stuart/FL
I just flip the bottle to vertical and it works. Sometimes when the bottle is almost empty I have to apply very (extremely) light pressure to coax out the drops. Checked multiple times and I don't get any variation. Do you clean the equipment after use and keep the tip clean? If you want to check technique split the same sample then test it. Different samples can have different results but I've never had even that happen. How old are your reagents and do you store inside?
 
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Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
24,022
SouthWest Alabama
Here's what I do.
  1. Gently squeeze the bottle while holding it upright.
  2. Turn the bottle vertically upside down while holding the 'squeeze'.
  3. Gently squeeze the bottle a little more until the drop starts to form.
  4. Continue gently squeezing until the drop falls from the nozzle.
  5. Keep slowly squeezing as each drop forms and falls from the tip.
  6. Once you've reached the endpoint, release the pressure on the bottle and that will suck the drop back into the bottle and there won't be any errant drips.
By doing the initial squeeze with the tip up, I find that I don't have drops forming and dropping before I'm ready for them to. Also with a little pressure on the bottle I have better control of the speed that the drops form.
 

markayash

Gold Supporter
Mar 21, 2016
1,883
Marrietta Ga
Check the expiration dates on your reagents? My PH solution in the 2006 kit wasn't expired but close and one test would should 7.4, I could rinse and do the exact same test again and get this weird looking color closer to 8. Bottle of R004 and it's consistent again.
 
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