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Friday, December 05, 2014

Answer to Last Month's Puzzler

UAS Construction Update for 12/05/2014

Answer to Last Month’s Puzzler

Last month we asked the question on why bubbles formed in the silicone window joint.  (See Post on Oct 31)  This question turned out to be more of a puzzler than I had expected.  We received several good theories and some not so good.  Here are some of the answers we received.

  1. Something left on edges of glass that reacted with the silicone causing gas bubbles.
  2. Calking gun not uniform and backing off a little and allowing an air bubble to form.
  3. Edges of glass not cleaned and the silicone lost “grip” of the glass when it cured. Thus creating small suction cup bubbles.  (See Oct 17 Entry for suction cup physics)
  4. Silicone emits gas as it cures.  When the Silicone is too thick the gas gets trapped inside the silicone joint causing bubbles.
  5. Silicone not stored properly causing it to go bad.
  6. The bubble ferry…… and it gets feathers caught when the silicone dries too fast.
  7. The glass has a film sandwiched in the center so it will not shatter if it breaks. This film is emitting a gas or is reacting with the Silicone creating gas bubbles.
  8. There is movement in the joint as it cures causing the bubbles to stretch or tear.  Movement can as little as someone leaning up against a pane of glass.

These answers came from Contractors, Architects, Engineers and the Silicone manufacture’s Product Manager.  All of these answers have a sense of plausibility. However, none of them address all of the questions in our puzzler, particularly why bubbles only formed on one side of the joint, why some sections had large bubbles and some small bubbles, why some sections had no bubbles.  

 2014 10-31 Feather Bubble 

                 Feather Bubble Suspended in Silicone

My theory is that it is a combination of answers 4, 7 and 8.  It may not be the cut and dry answer you were hoping for, but it’s my answer and I’m sticking to it. 

Good Luck on finals next week and lets all hope your exams have easier questions than “Why did bubbles form in the Silicone joint of the UAS Freshman Residential Housing conference room glass wall”.

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