Weird Science: it’s Friday!

Unbelievable as it may be for a scientist, it seems that I need to get out more.  The scientist larval stage, or “grad student” is rarely seen outside the labs, but last night I ventured outside my known territory in the company of a few other larvae.  When not in the lab, the larval stage of the scientist doesn’t tend to move very far, stopping to rest and refuel at bars for long periods of time before continuing on. 

One of my fellow grad students brought up something truly awesome last night: A study covered in Nature News on condom breakage.  Being the completely immature teenager that I still am, I shared this with everyone in my lab, and now I’m going to share it with you!!! 

Warning: pictures of condoms and the mechansim may be NSFW, depending on who you are.

White, Hill, Bodemeier. “Male condoms that break in use do so mostly by a “blunt puncture” mechanism” Contraception 77,2008 360-365.

Condom failure is a relatively rare phenomenon, about 0.4-2% for rubber condoms and 0.6-6% for synthetic, though the actual breakage number in a 1000 use study is usually less than 10.  Of course, numbers are easy to obtain, what is hard to figure out is WHY the condoms are breaking.  Is it lubrication?  Is it strength?  Is the user completely incompetant or naive?  Broken condoms are not usually returned (it is faily easy to imagine why) to the study centers, so it’s hard to study exactly why condoms are breaking, and so it’s hard to improve the condoms. 

So this study analyzed 972 USED condoms that had been returned as consumer complaints, washed and disenfected them (thank goodness!), and analyzed them for location of breakage and type of breakage that had occurred. They also conducted a survey to ask those who had not returned broken condoms why the condoms had broken.  Finally, to evaluate WHY the condoms were breaking, they made this:

Image

They refer to it as a “simple mechanical coital model”.  Unfortunately they fail to give dimensions for the model, describing it only as “physiologically accurate”, but to me that thing looks like it’s over two feet long!!!  At least it looks like that if it’s sitting on the floor and those are windows…I’m really hoping they’re not. 

 So what did they find?

Of the condoms they received, 474 were actually broken, 203 had some other defect (they do not say what), and another 290 were not actually defective.  Most of the condoms were broken in the “teat” area (the closed end), which is not surprising, as that is the part of the condom receiving the most mechanical stress.  But some of the condoms showed breakage, not at the tip, but as a kind of eruption through the side wall.

Image(A condom with ruptured tip)

They got about a 50% reply rate for the survey, finding that 97% of condoms had broken during intercourse, without any reports that “unusual or athletic practices were taking place”.   92% on users reported that they did not use any other lubricant (some, like petroleum jelly or mineral oil can weaker condoms). 

Looking for possible mechanisms of breakage, the researchers repeated stretched condoms over a “condom demonstrator” (which is used in condom factories and looks like a large test tube).  Repeated stretching did eventually cause breakage, and they noted that after several stretchings, the amount of force required to break a condom is actually fairly low.

They did notice that failures could be broken down into several types, though none appeared to be due to manufacture, and it is believed that “users are breaking normal…condoms because of the circumstances that arise during an individual act of intercourse”.  Eruption punctures, those causing holes in the walls or tip during use, appear to be caused by the penis pushing through the intact wall, a process they called “blunt puncture”. 

With the use of their coital model, they determined that breakage could be caused when the condom was stretched over the tip of the penis model (in other words, by not leaving a little reservoir of space at the end), with lots of lubrication inside, little lubrication outside, and a tight fit between artificial penis and artificial vagina.  By classification of the returned condoms, they found that 90% of failures could be accounted for by “blunt puncture”. 

Image

 

 In conclusion, the authors believe this information could help design new condom tests to increase efficacy, and also help make instructions more clear, so people stop breaking them.  So put your condom on correctly!!

5 Responses

  1. Interesting. I am assuming you do not wish this comment thread to be a place for a lot of people to describe in great detail their personal experiences on the topic…. ;-)

  2. Hahaha. Only if you happened to be one of the people taking the data with the coital simulator! :)

  3. On the subject of scale…
    Right behind the “interface” of the coital model is a UK power outlet which is probably around 8 cm in height. So the thing is almost certainly on top off a table and probably to scale. There’s also a wrench and other tools visible in the picture.

  4. I don’t need no da*n simulator ;-)

  5. Thanks Whodunnit! I still think that wrench looks awfully big…but the power outlet definitely helps. I was obviously not looking much at the rest of the machine…:)

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