Tinted Fermenters?

[mahonya1]

We all know that tinted, brown bottles are better for beer than clear and indeed green bottles, but what about the fermenter?? Can I assume that a tinted fermenter would be better than a clear one to protect the beer from light? If this is the case why are the majority of glass demijohns and plastic fermenters clear? And does anyone use pottery demijohns? Are there any disadvantages/advantages of using pottery demijohns?

 

[barls]

most of the glass demijohns are actually a pale green and the plastic fermenters i use are opaque plastic to limit light defusion.

 

[mahonya1]

most of the glass demijohns are actually a pale green and the plastic fermenters i use are opaque plastic to limit light defusion.

I was under the impression that green bottles are only marginally better than clear bottles, again assuming this is the case with demijohns.

 

[MHB]

Common plastic fermenters are made from High Density Poly-Ethylene (HDPE), thats the one called white but the colour is called Natural or Neutral in the trade, translucent would be a better description than white, the white ones that are opaque have a bunch of fillers added to them (from memory) Titanium or Tin Oxide.

HDPE is pretty opaque to the frequencies of light that cause skunking so I wouldnt worried about brewing in them.

Clear glass demijohns those big ones the Americans just love well frankly I havent got a clue as to why the beer doesnt get light strike in them, I think its a very reasonable question and Id like an answer to.

MHB

 

[brendanos]

Ray Daniels covered this in the Sep/Oct 2009 Zymurgy, and stated that fermenting beer will be too turbid to allow much (or any) light to penetrate the beer, and for the most part I agree with him. He suggests that any minute amounts formed during fermentation would most probably be volatised and blown off with CO2. He also explains that it is only a problem in very pale beers - ie amber, brown or black beers offer similar protection that the brown bottles do.

Beer will also not skunk til during/after fermentation as one of the requisite products of skunking (B2) has not yet been formed - so wort is ok in the sun (ie if you brew outside) so long as you ferment/store inside afterwards.

Incandescent lights do not cause a problem, though sunlight and fluorescent light can and will - given time, so if you use energy efficient fluoros in the room that you ferment/condition you might consider covering any pale beers after fermentation has begun.

 

[Wolfy]

The little man in my fridge turns off the light each time I close the door.
The way I look at it is that if you do use a clear glass or plastic fermenter it's not that hard to cover it with something or enclose it in something to prevent any adverse effects that light may have on it - better to be safe than sorry.

 

[jjeffrey]

You get skunking from exposure of iso alpha acids (formed from the boil) being exposed to UV light. If you're interested, this is what happens on a molecular basis:

For the geeks, most commercial beers sold in green or clear bottles don't get light struck (and I exclude Corona from this group) because they employ tetra-iso alpha acids.

Unless you leave your fermenter in the sun, it's not a problem. Incandescent and halogen sources produce sweet FA UV. A tiny amount from fluorescent lights, but the intensity is very low.

On bottle colours: brown glass blocks about 90% of UV light, green glass block about 15%, and clear glass about 8%. I have no idea about the transmission properties of HDPE or PET.

jj.