Sorry to bring up an old thread, but was searching this topic, and this was in the top 3 of googles search to my query!
Basically, in the UK, none of the available street stuff will dissolve in water, which is why snorting it is not a common ROA, and is highly ineffective (never given it a proper go, because I can get some very strong NO.3 (this is what is exclusively available, as in, unless you went on holiday and brought some no.4 back from abroad, no.3 is what the UK has on offer, period.) and i would not waste it by snorting it.
So this being the case, if you are in the UK, or anywhere else for that matter and have NO.3 (heroin base / brown powder that requires addition of citric for it to dissolve in water, which IV users must do to make it into a shootable liquid) DO NOT BOTHER TRYING THIS! IT WONT BE EFFECTIVE SNORTED AS POWDER, IT WONT DISSOLVE IN WATER, SO MAKING A NASAL SPRAY BY MIXING IT WITH WATER FIRST WONT MAKE IT ANY MORE EFFECTIVE WHEN SNORTED...!
I have no idea if this would work as I do not IV, but if you were to make it into a liquid, using citric, i.e.. using same steps to prepare for IV shot, then putting that in a nasal spray bottle, it just might work, but STILL, with NO.3 a bag in the UK is usually between 0.1 and 0.2, and smokers will smoke that all in the same 'session' as it were. And IV users will usually put entire bag into a shot (some may get 2 shots depending on size and potency of bag), but either way, whichever ROA, the user will generally use the whole (lets call it 135mg per bag) bag as quickly as possible. Basically a line would be the whole bag, and sniffing that all at once would not have anything close to the effect of smoking it...
So even if you were to dissolve the NO.3 using citric, and even if this did work as a nasal spray, it would take a whole lot of sprays to get it all into your nose - and if done quickly, there would be too much liquid and it would either drip straight down throat, or fall back out of nose (doesn't matter which, but it is too much for the nose to absorb at once, so it would be a waste.
IF YOU HAVE NO.3 - SMOKING IS MORE EFFECTIVE DEFINITELY.
IF YOU HAVE NO.4 - INTRANASAL IS MORE EFFECTIVE DEFINITELY. ALSO NO.4 GENERALLY WONT SMOKE WELL, IE. IT WONT 'RUN' ON THE FOIL
What I am trying to say is, the stuff that is good for snorting is NO.4, as it dissolves in water without anything added, not even heat is required. And for snorting not to be a waste, it needs to be strong NO.4 as well for this method to work. This is because if it is strong NO.4 you would not need to snort a line anywhere near 135mg to get the desired effect. Depending on potency and an individuals tolerance, between as little as 10mg (china white from golden triangle) and 50mg (some pretty good NO.4) is all thats required to get an effect, and again tolerance depending this amount could provide a strong high. Even less for IV (I am guessing).
I am not saying all NO.4 is stronger than NO.3 / base H, as NO.4 can be cut to fuck just the same as any drug, so in some cases, a bag of NO.3 will have higher percentage heroin content than a bag of same weight of NO.4. What I am saying is that NO.3 is not designed for snorting, or even REALLY for IV as it needs additional chemicals to make shooting it possible. It is made for smoking, which is what the vast majority of the Afghani addicts will do. NO.4 IS designed for IV as it requires nothing apart from water to make it shootable, and because of its water solubility, it is also completely suitable for snorting as it will get absorbed in the mucous membranes of the nose.
SO - IF you have NO.4 I would suggest doing this in small amounts at a time. e.g.. a lines worth dissolved in as little water as possible, which won't be much if its fairly pure, put this into an empty and washed out nasal spray bottle and to dose spray the mist continually until the container is empty again (won't take many sprays, and will help absorption (many people sniff a bit of water before and / or after sniffing a line to aid absorbtion), I think having it already mixed like this will be more effective - in fact it IS more effective!).
I would NOT pre mix a load in like a half full bottle though. Would be too hard to judge amounts needed of water and H, and also as mentioned it could degrade. I would just do it a lines worth at a time (which isn't a hassle, as when sniffing H, unlike coke, you don't sniff line after line all night, but rather every few hours, so a decent lines worth dissolved into as little water as possible, every few hrs, or however often you would sniff a line, do this instead. A few sprays and its finished, all one after the other in alternating nostrils.
I also think its worth mentioning that this is likely very effective as a harm reduction technique for sniffing H. It avoids the raw H hitting your nose dry, which over time would cause damage. This method will definitely soften the blow in terms of damage to the nostrils (REMEMBER TO SWITCH NOSTRILS AS WELL WHEN SNIFFING ANYTHING!)