Most candle spells say to let the candle burn out completely. This is usually why spell candles are fairly small and will disappear after a couple of hours. The candle is a material component of the specific spell (especially if you dress the candle with markings, oils and herbs), so the candle's energy is helping to fuel the magical work.
However some spells require you to burn sections of a candle over a number of days, then let it burn out completely on the final day. You can buy sectioned knobbly candles for this purpose.
Typically if one dresses the candle adding energy with oils, and herbs which correspond to the working the candle is left to burn down to release the added energy.
If one is using the flame alone as a meditative point focusing energy into the flame the candle can be put out if wanted.
Some suggest in this case not to blow the flame out if you are looking to attract things, as this will blow what you want to attract away. In this case one can use a candle snuffer.
In the case of banishing it can be appropriate to blow the flame out.
And, like stated there are seven day candles or large pillars which can be used for a working designed to last for a number of days. One can either blow or snuff these out and light again later to continue the working.
Essentially it depends on the working whether you let the candle burn or blow it out. Workings utilizing the flame as a focal point can be put out. If one wants to dress the candle, adding their energy to it, it is recommended you let it burn down as much as able to release the energy for the spell working.
I really believe it depends on the spell your doing
For example if your doing a blessings spell it is said to not blow your candle out as it not the best to blow out your blessings With that being said always to remember to practice fire safety It is never 100% safe to leave a candle unattended
Hope this helped best of luck
I prefer to use a candle snuffer. In most 101 books they generally advise you not to blow the candles out. There are many reasons why people use a snuffer over blowing them out or letting candles burn completely. Some folks may say that if you blow out the candles you are blowing all the positive energy away. Letting a candle burn out completely can take a long time, and depending on the size may not be safe. Some larger candles you are advised only to burn for about 2 hours at a time. It can prevent tunneling and the wick 'mushrooming'. Allowing large candles to burn out completely as I mentioned is time consuming and you may end up walking away, leaving the candle unattended which could cause potential fires. That all being said some spells will require you to have candles burn out completely. I would suggest using tea light candles or those small spell candles/chime candles as they are small.
You can purchase candle snuffers online or in stores. They can be hard to find and can be in the most random places. If you are unable to purchase one you can use other items in the mean time to snuff out your candles. I have some old bath and body works candle jars and lids, the lids are great for snuffing out candles of any kind. I've used the lid to my cauldron as well which is cast iron.
Depending on my mood I either use a candle snuffer or blow it out. I've always thought blowing out candles was a lot like making a birthday wish, putting my own will into the spell as it were. However, if it's devotional, a snuffer is the way I usually go. Letting things burn out, unless it's a bonfire or fireplace, doesn't sit well with me. I'm not one for single-use candles.
I believe the idea comes from the Persians, who recognize fire as holy and think of it as disrespectful to blow out a candle.
Just lick your thumb and pointer finger and snuff the flame like that. Works in a pinch