1. Wait at least a month after the healing time to stretch a new piercing.
2. Only go up one gauge/size at a time.
3. It should never hurt or bleed. It may feel stretched or slightly tingly. There will be some sensation, but it should not be pain.
4. Always use ample lubrication. Water based is best, but some people prefer oil based.
5. Do not "dead stretch". This is stretching without using a taper, crescent, pincher or other instrument that gradually increases in size. Tapers work really well. I've found that the stainless steel ones with a dimple or hole on the end to accommodate jewelry work best.
6. Times in between stretching healed piercings- could be one month (at the least), but more likely is longer than that. Listen to your body. If it hurts, or is not going in, DO NOT FORCE IT. You may end up with a blowout and permanent damage to your piercing.
7. Choose appropriate jewelry. If you are stretching lobes, you will need either a barbell, CBR, CBB, pincher, or single flare plug. You will not be able to put in a double flare plug right after stretching, because the flares are often .5 to 1 gauge larger than the actual gauge of the jewelry, which is measured in the "saddle" part of the plug. Do NOT use KAOS silicone skins to stretch-even KAOS tells you that they are not ideal for stretching. I've found the cheapest, safest jewelry to be single flare of coulourfront glass plugs.
8. Cartilage is notoriously difficult to stretch in most people. This is one instance where I would consult a piercer.
9. Some piercings are known to self stretch, but not on everybody. Septums, VCHs, HCHs, Frenums, Prince Alberts....there are numerous accounts of these piercings self stretching.
10. In general, if you are stretching lobes and you want them to not get "past the point of no return", you should stop at a two or zero gauge. Commonly, stretched lobes that haven't gone past a zero will close back up if you take the jewelry out. If you are not ready to be able to see through the holes in your ears for the rest of your life, do not stretch beyond a two or zero. This is a general rule and can be different for everybody.
11. Stretched piercings do reduce the chance of tearing due to accident, and in some piercings may reduce the risk of migration. Check with your piercer to see if your piercing falls under this category. Ideally, you will have been pierced a the minimum recommended gauge for your specific piercing.
Starter's guide to stretching
(BTW, it is easiest to stretch after a hot shower to loosen the piercing.)
You will need-
Appropriate jewelry only one size (gauge) larger than what you are
Lubrication
Taper
Paper towel to wipe up extra lube
Remove old jewelry and uncrew/open new jewelry. Have everything in front of you, and do not do this over a sink.
Lubricate taper.
Gently and slowly slide the taper through the piercing.
When you get towards the end of the taper, line up the new jewelry with the large end of the taper. Your jewelry should either be flush with or sit slightly inside the end of the taper. Follow the taper through with the jewelry.
Screw new ends on the jewelry or insert captive bead.
Wipe away excess lube.
Done!
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What bash said....
(There, now I don't have to keep typing it)