I remember when I tried the water soluble thread on a trapunto: I had trouble getting the needle threaded. OK - what do we do when we can't thread a needle? WE LICK THE THREAD. Not such a smart idea when using the water soluble.
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My eyes have grown old with me, so when threading sewing machine needles, I put a little bit of white paper behind the needle and instantly i can see the hole. Also good is a touch of White-out on it, that is more permanent.
That works best for me.