why are sap sacks colored

[wvsugarshak]

does the color of the sap sack make any difference. I have only see blue. does this help keep the lite out or keep the sap cooler in the sunshine. hard to tell when you sap is yellow would be nice if the bag looked green then . will if someone knows a official answer please pass it along

thanks

wvsugarshak

[markcasper]

When they were introduced in the late 1950's in Wisconsin, the blue color was touted as having bacteria killing qualities when sunlight penetrated the bags. I use only clear bags, not blue. The darker color does help thaw ice if your in a cold bush.

The bags, whether blue or clear, always grow black and pink spots towards the end of the season, so I guess the bacteria never got killled.