During a recent brew, I was using my refractometer and getting readings all over the place. one minute I would get a reading of 21 brix, and the next minute 19 something. I had lost my little dropper that came with it, and was just dropping a little on my view plate with my stir spoon. Could the quantity of wort being put on it cause such a variation of discrepancies?
One thing that must be considered when measuring hot wort is evaporation. Repeatable measurements is important when measuring the sugar concentration. I like to be able to repeat my measurement. Sometimes I have to take several readings in an effort to achieve that. I use the dropper and act quickly while measuring with my refractometer.
The quantity should not affect it. Temperature might. If you’re measuring hot wort, a small quantity could cool quickly, and give you a different reading than a larger amount.
If they were the same temperature, I would expect no difference.
I finally gave up on using my refractometer for just that reason, Grant. I should probably get it out and see if I can figure out what the problem was.
I flip the cover immediately with a flick of my wrist. If you find or buy some more disposable droppers (cheap on web) draw up just a couple drops. It will reach room temp quickly. I do mine inside instead of the brew area where it can be 20+ degrees warmer.
How well was your wort mixed? It might have pockets or layers of different volumes of sugar (for a awhile at least). Make sure it’s stirred well before you take a reading.
For boiling wort I remove some using the dropper that came with my refractometer (I know you said you lost yours). As soon as I suck the wort up, I cover the open end of the dropper with my finger and plunge the bulb into a glass of cold water. Then I take my readings. It seem to work for me but YMMV.
Paul
What about solids in the wort, could that affect your readng ?
I too lost my dropper and this thread reminded me to find another. Just picked these up:
http://www.amazon.com/gp/product/B000EFMLQ2
There are many other options out there, this is just one example.
AFAIK, nope.
How well was your wort mixed? It might have pockets or layers of different volumes of sugar (for a awhile at least). Make sure it’s stirred well before you take a reading.
I do not think this is what is causing the variations. The readings were taken well into a vigorous boil. I am planning on buying a dropper before the next brew. Thanks for all your thoughts
Grant,
Good topic. I agree with the others–stir well, obtain a few drops with your pipette, place a few drops on your room temp refractometer and put the cover on right away. Random particles don’t matter.
My first plastic pipette was put away after a nice brewday with several refractometer readings and any extra “samples” going right into my mouth. When I opened up the case for the next brewday, the pipette was all moldy. Needless to say, I tossed the pipette in the garbage.
To prevent a recurrence, all subsequent pipettes have been quickly rinsed with water and sanitized with StarSan before being put away at the end of the brew day. No need to keep replacing plastic pipettes, unless you lose them.
If you really want to know more about the refractometer, we had a good discussion about this earlier this year.
http://www.homebrewersassociation.org/forum/index.php?topic=2307.45
Pippette??? Mine got moldy the third of fourth time I used it. Since then, I just dip my thermometer into the wort and let a drop of two fall off the tip onto the refractometer.
Moldy? Rinse with sanitizer before putting it away, or buy a 12-pack of pipettes. 
Glass eyedroppers are cheap and can often be found at your local pharmacy. You can take them apart to clean them, unlike the cheap plastic thing that comes with most refractometers.
I just stick my brewing spoon into the boiling wort and let it drip onto the refractometer. Why buy more stuff?
When I do that I get an elevated reading due to evaporation.
That’s why corky regularly gets 110% efficiency ;D
If you scoop up a bunch and drip it on there I think evaporation will be minimal.
I thought it was the BLUE cooler mash tun.
Nah, the BLUE cooler mash tun is only good for a 10% to 15% efficiency improvement. I’ve found, through numerous brew day experiments, that any additional increase in efficiency is directly related to the quantity of home brew consumed.
+1 to the eye dropper, and I let it cool to room temp. Once I started doing that my readings became consistent and reliable.
Isn’t the point of this hobby to buy as much stuff as possible and come up with reason to brew with it?