Saturday, December 20, 2014

Cloning a Golden Dragon, Part 6 - Fermentation Continues

In Part 1, we talked about how I harvested yeast from four bottles of Gulden Draak ale like the one pictured at the left.  In Part 2 and Part 3, I talked about raising enough of that yeast to pitch into a wort to make a clone.  In Part 4 we discussed brewing the clone and showed steps in the process.  In Part 5, fermentation had begun.

I had expected to be transferring the beer from the primary fermenter to the secondary this weekend.  As it turns out, that did not happen.

I've been monitoring the gravity of the beer using a refractometer since the original wort was brewed on December 13, 2014.  It started at 1.109.  On the 15th, that dropped to 1.085.  On the 17th, 1.080. On the 18th, 1.078.  Today, it's showing as 1.075.  Since the yeast is still actively chewing away on the sugars in the wort and we're nowhere near the final gravity I'm hoping for (1.026), I'm going to let the beer continue to ferment.  I want to give it every chance to produce an excellent and complete clone of the original Gulden Draak.

Earlier, I mentioned a refractometer.  If you haven't brewed a beer of your own, and even if you have, you may never have heard of this device.  You might find it interesting.  A refractometer uses a prism to measure the amount of dissolved solids (in this case malt and sugar) in a liquid.  It looks something like a light saber from Star Wars:

To use a refractometer, you start by taking a very small sample of your wort or beer-in-progress.  In my case, I do this by opening a valve at the bottom of my fermenter:

It doesn't take very much wort for the refractometer to do its thing.  A couple of drops is enough.  I collect that with a pipette:

Then, I put it on the prism of the refractometer:

Next, you flip the little plastic lid down and hold the refractometer up to a bright light source, preferably a sunny window.  Inside the viewfinder end, you'll see a blue line at the point corresponding to the gravity reading for the sample.

I realize that it's hard to see the blue line in this photo, but it's right around the 20 on the left-hand side.  Getting a photo of a refractometer reading with a cell phone camera under less-than-ideal viewing conditions is tricky, to say the least.

In any case, some interesting things to know about a refractometer...

When properly calibrated, they make measuring the gravity of an unfermented wort very easy.

When alcohol is present, as it is once you've pitched yeast into your wort, they start becoming rather inaccurate.  (I didn't know this until very recently!)  Fortunately, if you own a hydrometer (which I will soon) you can adjust for this.  You use the hydrometer to take a measurement, then use the refractometer on an identical sample.  Do enough of these comparisons, and you'll be able to use a mathematical formula to adjust your refractometer readings to closely approximate a hydrometer.

A question many home brewers ask is "Why would you want a refractometer when a hydrometer is a much more accurate measuring device?"  For me, the answers are simple.  It's common for home brewers to break hydrometers, as they're fragile instruments made of glass.  I'd rather not use any fragile instruments in my brewing activity.  More importantly, a hydrometer may need 6-8 ounces of beer from the fermenter in order to give a reading.  The beer that you use with the hydrometer can't be returned to the fermenter without risk of contamination, so you either have to toss it (which is wasteful) or drink it flat and warm (which isn't appetizing).  If you take several measurements during fermentation, you can easily waste two or three bottles' worth of beer with a hydrometer.  A refractometer needs only a few drops of beer for each sample.  You could perform a dozen measurements with it and not waste as much beer as with a single sample for a hydrometer.  Since I tend to brew smaller batches (2-5 gallons) I'd rather not waste any more than necessary.

When my hydrometer gets here, I'll talk about the adjustment process for ensuring that you properly account for a refractometer's shortcomings when a sample contains alcohol.

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