Blow off with every starter?

The last 5 starters that I made have all had a blow out and I can't figure out why.

I am using Pilsen or Extra light DME @ 1 gram per 10ml of water (120g for a 1200 ml starter). I boil it for approximately 5 minutes and put it into a 2000ml flask with a stir plate and a foam stopper. In the morning there is yeast all over the out side of the flask.

I used 3 types of yeast (1056,1272 and WLP001)

I've had the same result when I just you aluminum foil too.

Any ideas?

I stepped up a starter once and it overflowed. Since then, I put a towel under my stirplate and won't make more than 1000 mL at a time. I make my starter the weekend before I brew. When it's finished I put it in a 2 liter pop bottle and keep it in the fridge. If I need more than a liter, I just make a second starter then put it in the same pop bottle. I usually decant some liquid before I add the second starter and I always decant before I pitch.

I've had this same problem with a 2000ML flask when making the large starters for bigger beers or Lagers. I just cover the top with sanatized foil and wait until the blow off has subsided and then put it on the stir plate.

Get some Fermcap-S, problem solved, or should be anyway. Use it when you boil up the DME and it will help control the fermentation of the starter as well.

That's a good idea