Refractometer hell

[BS]

My refractometer measures in Brix, so I wasn't inadvertently reading Brix and thinking that was my OG. An 8 Brix OG would be pretty pathetic!

I will collect a small cup of wort next time and let that cool down. The evaporation effect makes sense as an explanation as to why the reading was so far off. I also need to reset my system efficiency in ProMash, obviously.

[Yorg]

The real advantages of using a refractometer in the first place is that you only need a small sample that will cool quickly, as opposed to a hydrometer.
Rather than use a cup, get a turkey baster or smaller but similar thing for measuring medicine - similar to the earlier suggestion. Glass will cool a decent sized sample ( about 15-20ml) quickly.
I have had similar problems when using the plastic pipette that came with the refractometer - I suspect the sample size is still too small, and enough evaporates even from the pipette mouth.

[Brandt]

Make certain to rinse and dry between samples. Any redidual rinse water on the lens can affect the reading. If you're taking a sample of cooled wort or beer, you may need more than a few drops to "rinse" the sanitizer you used on your sample taking device ( spoon, pipette, etc.)

During brewing I just pour some boiling wort over the lens to take my reading. I don't even bother with the plastic sampler. It cools almost immediately so I don't think evaporation is an issue, or at least the methods are consisitent so I'm getting relative readings.

[Eagle Creek Brewer]

Have you figured out your correction factor? Wort is not a straight across number when using a refractometer.

You might want to look at this link and the associated spreadsheet. It does work great for me.

http://morebeer.com/learn_vids/vids_refract

[Elbone]

Well-

Specific gravity obviously can't decrease during the boil so it has to be a sampling error of some kind.

Did you stir viger-rosely before you took the pre-boil sample? I have found that wort fresh in the kettle from the mash tun can become really stratified. Always make sure your wort is gently mixed to homogeneity before sampling. I usually bring it to a boil for a short time to mix and then take a sample for the refractometer.

[Brandt]

Always make sure your wort is gently mixed to homogeneity before sampling. I usually bring it to a boil for a short time to mix and then take a sample for the refractometer.

Seconded! I sample the runnings when I think I'm near the end of sparging, just to make sure I'm not getting too low in sugars (tannin extraction due to pH increase/ dilution). Then I wait until full boil to take my first gravity reading. It seems like the boiling action really homogenizes everything.

[Mylo]

Have you figured out your correction factor? Wort is not a straight across number when using a refractometer.

You might want to look at this link and the associated spreadsheet. It does work great for me.

http://morebeer.com/learn_vids/vids_refract

Wort is a sugar solution, and is fine to read with Brix pre-fermentation. The spreadsheet you reference is for using the refractometer during fermentation.


Mylo

[Eagle Creek Brewer]

Have you figured out your correction factor? Wort is not a straight across number when using a refractometer.

You might want to look at this link and the associated spreadsheet. It does work great for me.

http://morebeer.com/learn_vids/vids_refract

Wort is a sugar solution, and is fine to read with Brix pre-fermentation. The spreadsheet you reference is for using the refractometer during fermentation.


Mylo

You still have to figure in your correction factor. Everyone's may be a bit different but usually it will be consistent once figured. Wort contains substances that will skew your original reading. If you look at the macro on the first reading in that spreadsheet it will show the math they used. Promash also has some explanation also. It may not be his problem as his numbers went the wrong way, but to get an accurate reading from a refractometer to sg you need to know that number.