A cap from a bottle of shampoo went down the drain. It will not plunge out of the drain and it is slowing the draining of the tub. How can I disolve it or make it come up or go down.

Is the cap tight in the drain or just can't get a hand on it. How far down is the cap.

You won't be able to disolve the cap. You will either have to snake the drain, or get into drain to remove the cap. Please answer ac101s question, can you see the cap. Im guessing that it is caught either in the waste and overflow assembly(where waste meets overflow) or in the trap. Please let us know where you think the cap is, and we will try to help you remove it, or push it downstream to the main sewer.

Here is a trick I use in a case like this, but it all depend on the circumstance. Take a wire coat hanger, straighten out the hanger, bend a hook on the end of the end heat the hook over a flame, push the hook through the cap and turn it a 1/4 turn, Let it cool and now pull the coat hanger out, it should have melted a hole in the cap and as the cap hardened it should close around the wire, and you should be able to pull the cap out.

If this helps please let me know.

Remove trap and shake it out.

Please let us know if you can actually see the cap. If so, letmetellu has a very good chance of winning this one. If cap is stuck just in bottom of shoe, you can also try running a sheetrock screw into the cap and pull it out with the screw. Please let us know how things turn out, or if you need more advice. If you can't see the cap, then do as Milo suggested.

The easy way is a good shop vac hold a towel over the overflow put the hose over the drain as tight as possible and turn it on should suck it out

is the cap tight in the drain or just can't get a hand on it. How far down is the cap.
It is down too far to reach or even see. Probably several feet down.