Both hop spiders and bags are very inefficient in my experience. The surface area of the mesh is very low compared to the surface area of the hops so utilisation will suffer. This can be reduced by giving the bag a good squeze or if you use a bag that is significantly larger than needed for the hops so more wort can get into the bag and mix with the hops. I have not had great success with spiders as they just clog up however with my current system I have started using a large basket, the type you get in the Clawhammer system. I use this as I have a plate chiller and really want to make sure I minimise or even prevent any hops getting through to the chiller. I've tried in-line filters in conjunction with the false bottom and its isn't completely effective but the hop basket seems to work fine. It's basically a very large hop spider but works due to the massive surface area and you get free flow of wort through the basket through the boil and hopstand/whirlpool. Also I transfer the wort into it so it filters out any grain that gets transferred. Pics below from my last brewday...
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After transfer only hop matter is left. There is a couple of inches of space below the basket to allow for the heating element and by the time all the wort has transferred to the fermenter the hops feel very dry so any absorbed wort drops out under gravity. Previously with hop spiders with alot smaller surface area and little flowing wort the hops would clog the mesh reducing utilisation and preventing any wort captured in the hop spider....the wort you really want as its super concentrated with the hop infusion, wont drain out through the few mm of hops coating the side of the hop spider. The much larger surface area of the basket and free'er flowing wort through it prevents the hop build up on the sides. There is also a slight dome shape to the hop pile at the bottom of the basket from the whirlpool, so even the whirlpool has an effect through the basket.
And clean up is a cinch...just scrape out as much of the hops you can, then turn upside down and hose down the top and sides and it comes out clean as a whistle and really for a soak in hot sodium percarbonate.
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