I tried just putting pureed, raw rhubarb through a fine sieve to see if it would work as well as putting it through a jelly bag. It looked pretty cloudy to me, so I decided to try putting it through a coffee filter. (I bought a package of coffee filters on vacation a couple years ago and don’t actually use them at home.) It takes a long time, but of course you can just walk away and let it drain. And the juice is a beautiful pink colour, as opposed to the green I get using the jelly bag.
My garden is still producing lots of rhubarb, so this is great to know. It should make my next batch of rhubarb jelly prettier, too.