I bought a bottled orange juice. I got drinking straw and placed it in, it sank well down to bottom. After a day, I bought bottled juice again. Got one drinking straw and placed it in. The straw floated. It does not really matter whether a drinking straw floats or sinks. The more important are : it should be clean and able to serve its sucking purpose.
Placing floating straw in a glass of juice is a bit annoying. The straw will float and often fall on table. Noticed that most restaurant and fast food chains never served drinks with straw in. The straw is placed near the glass. The customer have a choice to use or not to use it. If the straw fall, then it is customer’s fault. It should be placed in the drink when the customer will actually drink it. About 1/4 of the content should be consumed immediately to prevent straw from falling out. The emptied glass portion will served as straw support.
I wish all drinking straws are made to sink so the hassle will be eliminated.
Here are some facts. Drinking straws that float are made of polypropylene plastic. Polymer that is generally recommended for food contacts. They are stronger and more durable. On the other hand, those that float are made of polystyrene.
Nowadays, most drinking straws are made to float.
Update as of May 26, 2012. A self conducted experiment showed that some straws might be made of LDPE, low density polyethylene. Read, “Popular Drinking Straws Are Made Of?“