Do you use detergent when prepping.

brand new nappies? I was going to do a couple of washes to start increasing the absorbency (bamboo stuff) and just wondered if the detergent was necessary or not.

I would. Some of the products that they use on fabrics during the manufacturing process needs to be washed off so that the nappies can absorb the maximum amount of wee. I don't know if they will come off with water alone.

I'm just starting with some bamboo now. First time I've washed them actually but I didn't have enough white stuff for a full load so thought I'd throw my small bamboos and bamboo inserts in there.

So yes, I'm using detergent as its in with my normal washing. (Bold 2 in 1 though as I didn't want to use my normal softener.)

yep, but 1/3-1/2 the usual amount of washing powder

I prewashed mine 3 times before use (they dont reach max absorbancy until 10+ washes, but 3 is enough for prewashing)
You dont need to dry them inbetween prewashes - just turn the washing machine back on.
You dont need to do a long cycle either - just a short quick wash is enough!