A cold shot is a solution of heroin dissolved in water that was not boiled. There are two reasons that users inject cold shots: necessity and frugality. Sometimes users don't have easy access to a flame, so they spend a lot of time mixing heroin in cold water. More often, users think they are wasting money because boiling the solution causes evaporation and thus loss of money.
In general, it is a bad idea to inject cold shots. The minor benefits do not compensate for the major benefits of boiling the water when dissolving the heroin.
White powder, as well as black tar heroin can be dissolved in cold water. But it can take a long time mixing to do so. Most users heat their dope because it is the fastest way to get it dissolved. Heroin, like most things, dissolves much faster in hot water than cold water.
Heating does not allow more heroin to get into solution. This is because the solution is cooled before injection (and if it isn't, it should be). If the higher temperature did allow more heroin to be dissolved, the extra heroin would solidify out of the solution as it cooled.
Boiling your heroin solution makes it less dangerous. Although boiling won't kill everything harmful that might be found in any given sample of street dope, it is helpful.
Bacteria can live in samples of heroin. Bringing the solution to a boil will kill most kinds of bacteria This means that if you boil the solution, it will be safer to inject.
If you have had heart valve problems, or pins from something like a broken limb, you should definitely boil the solution because these are places where bacteria readily grow. For more information, look up endocarditis in a disease book or in my book, Heroin User's Handbook. It is also discussed in the disease article on this site.
Boiling will not kill all kinds of bacteria. In particular, it will not kill any spore-forming bacteria--like the flesh eating bacteria. Never forget that using any black-market item is dangerous.
Boiling also incapacitates viruses. I recall in Portland that Hepatitis C was rampant among cocaine users, but not heroin users because the cocaine users were not boiling their dope. Again, boiling is not a perfect defense, but it is an easy way to make heroin use less dangerous.
Boiling does waste a certain amount of dope because it gets vaporized. If you boil your solution, don't do it for long. Bring it to the point at which it just begins to boil and remove the flame. Anything that isn't killed by that will need to be boiled for far longer than is practicable.
The bottom line is this: boiling makes the dope dissolve faster and it makes it less dangerous to ingest. The down-side is that it also wastes some of the heroin--but not that much if care is taken.
Conclusion: Avoid False Economies
It is not necessary to use to boil a heroin solution, just as it is not necessary to use a cotton to filter heroin before injection, either. But it is foolish to not do so (cotton actually filter out some bacteria strains because they are large--use a tight cotton ball for filtering). Not using a cotton; not boiling; these are false economies. Doing so may save you a dollar, but you can only spend it if you're alive.
A few people on alt.drugs.hard have pointed out that cold shots can be safer than boiled shots because boiling allows the final solution to contain more of the adulterants found in heroin samples. This is true, but two points must be considered.
- The solution should never be injected hot. The solution should be cooled first. This will cause these adulterants to separate out so that their concentration is no higher than it would be if the solution had never been boiled.
- Most of the things that heroin is cut with are more soluble than the heroin itself (e.g. coffee and sugar). Thus, this isn't much of an issue.
Regardless, injecting any street drugs has dangers associated with it that cannot be eliminated.