Refractometer problem?

Can refractometers be damaged if they get too hot? I accidentally left mine in the sun for ~30 minutes and now I'm wondering if it's the source of my problems. It's one of the those cheap ones you can get on eBay shipped directly from China. I brought it inside to let it cool back down to room temperature, and then re-calibrated it to room temperature... but then my problems began.

Back story: I've used a refractometer for my last 5-6 all-grain BIAB batches and always check my pre-boil OG with it. My mash efficiency was consistently in the 75% range until my second-to-last batch, which all of sudden registered around 55% based on my refractometer OG reading! I added a bunch of DME to compensate and wondered if I got a bad crush at my LHBS...

My last batch I had the same problem, super low pre-boil OG. Again I added a bunch of DME. I had the grains crushed at a different shop, so I'm now looking at the refractometer as the source of my efficiency woes.

In this latest batch, a bit of strangeness is that my OG post-boil actually decreased (based on my refractometer) relative to pre-boil. This was based on a sample of leftover wort in the bottom of the kettle. Is it possible that my refractometer is at issue, or am I doing something completely wrong?

Your best bet would be to run some comparisons with a calibrated hydrometer.

It's entirely possible that both shops had crappy crushes. It's always good to have a hydrometer on hand if you already have one. They are pretty cheap.

Homercidal said:

Your best bet would be to run some comparisons with a calibrated hydrometer.

It's entirely possible that both shops had crappy crushes. It's always good to have a hydrometer on hand if you already have one. They are pretty cheap.

Click to expand...

Will do, thanks. Now that I think of it, the first few all grain batches that gave me 75% efficiency all came from one source, and these last two odd batches came from different sources. If my refractometer checks out I'm really going to consider getting a mill.

I built my own, and now that I have one I could never want to use an LHBS crush on a regular basis. They are worth it in savings over precrushed grain if you brew a lot, and for being able to crush when you want.