Screen Printing Blunders : 1st Burning Failure

I tried burning one of the designs on an emulsified screen tonight. My light box, which I got from my screen printing tutorial, is designed for 8 to 10 minutes of exposure. A print-out of the design serves as the film positive. Using acetate is the best, though expensive, because it is transparent. Vellum or tracing paper is translucent and is much cheaper than acetate. But I don't have tracing paper yet so I just used ordinary paper as what my instructor did.

After the burning time of 10 minutes I looked at the emulsion in the dim light of my room and saw no impression of the design on it. I took the frame outside and blasted it with water using a garden hose. If it were a successful burning, the emulsion blocked by the black ink of the print out should be left uncured and be washed off with water. But it didn't.
No emulsion was washed out - it was a completely cured. That could only mean that it was over exposed to light. So I tried burning another screen, this time for just 8 minutes. The same thing happened and it made me upset. I called my instructor but he was out of reach. Then I went online and checked out t-shirtforums.com, a website he told me about before, to find out where I went wrong. I tried registering but their Solve Media (device for preventing spam robots) is faulty - no image appears. Even sending a message to the admin requires Solve Media. How can anyone register? Anyways, I could still search and browse the forums without registering.

So there I learned that the type of emulsion that I used (diazo), which came in the package of my tutorial last year, has a short shelf life and has to be stored in a refrigerator! I also learned in the that some emulsions are pre-mixed with sensitizer (chemical that makes the emulsion sensitive to light). I really don't remember my instructor telling me this important information - and that upsets me more.

I'm aware that screens can be reclaimed (can be removed of emulsion for reuse) so I searched the forums if a special fluid is available. I've read that some people use bleach to reclaim screens, others use lacquer thinner. But in a forum cluttered with posts that has nothing to do with the subject of reclaiming, I couldn't find the effective way of how it is done.

So I have 3 ruined screens and 16 days until April 1. There's nothing much I can do tonight. I might as well call it a night.