I gotta say this because of all the mis-information from people that say it doesn't work. YES smoking oxy's will get you high. It works, it gets you high, tastes like shit and the high is gone within 2 hours MAX. I am an addict, I have tested this with the morning sick and it got me off craps but didn't get me fixed, even after smoking 2 80mg pills between myself and a friend who was trying to help. Normally 40mg via IV, oral or nasal would fix me up just fine for about half the day. This helped me to prove my personal findings which I discuss further down this post about how your lungs absorb less and less with each hit etc.
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OK, now to answer your question:
Trying to hit the remains or "clean up" is pointless, scrape your tutor if you are that desperate. 99.99999% of the oxycodone is vaporized on the first pass unless you leave a bunch of caramel looking shit, and even that has little to nothing in it. All you are doing when you "clean up" a foil is putting more binders, carbon and SHIT into your lungs.
So in short don't bother cleaning up a foil, it's completely pointless.
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Some additional information to STRONGLY consider:
After doing a bit of personal research amongst friends and reading online the past 5 years or so, I have found that after the 4th or 5th hit from smoking oxycontin, your lungs absorb less than half of what actually goes in (yes no matter how long you hold your hit in). Argue all you want on this one, but think about it - fill your lungs with binders, polymers and other garbage and expect them to absorb like they were before you smoked all that gummy nasty filler? -NO-, it's a really simple concept and here is a great analogy - imagine a pot pipe with a screen that is fresh, the pipe smokes great. However, after 2 or 3 bowls it gets harder and harder to get a good hit out of it. You can clean or replace a pipe screen, you cannot clean or replace your lungs. There are only a handful of drugs that really do well via smoking.
I have found that people smoking oxys are usually inexperienced opiate users or kids who have way too much of their parents money to blow on pills. If you take the same amount that you would normally smoke, and insufflate (thats snorting to you n00bs) it, you would probably puke from getting too high. I have seen this happen many o time from watching people who normally smoke, don't have foil and decide it's all the same and rail up the same amount they would smoke, get waaaay too high and end up getting sick, puking and nodding out like they were drugged up for an operation (the way a good high is supposed to be minus the puke

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Sry for the long winded post, it just sucks to see people waste so much of a drug because it's "fun" to smoke. It's only fun until you permanently damage your lungs from filling it with polymers/binders because you think "it's the best way and its a pleasant euphoric high".
Trust me, and anyone on this forum that will back me when I say you will have permanent lung damage if you are a daily user (smoking) for more than 60 days.
I have seen perm. lung damage from 3 different friends of mine that used to be smokers. Now 2 of them are unable to smoke anything, cigs, pot, hash, meth, nothing, because of the pain associated with it from all the scarring that was done by the binders in the pills. One of these friends is a close buddy and his doctor was HORRIFIED at the way his lungs looked from the X-ray when he went in the ER. He had a bad cough that manifested into pneumonia from poor lung function. Even after 3 years he still sleeps with a C-Pap machine and will have to the rest of his life at 26 years old.
I only pass this information on to help, not to bitch or complain that you are wasting drugs, it's your money do what you want but consider this: You are wasting your ONLY pair of lungs by putting particles in them that your body cannot naturally break down. Not rocket science my friend, only common sense. I am a seasoned opiate veteran so I feel the info I am sharing is valid and helpful.
If I didn't care, I would not have posted this. If I am off on this one, anyone please feel free to correct me.
-Noddy