Gold and dark rum is aged in old whiskey or bourbon barrels which are charred on the inside, sometimes they use new charred barrels as well.
why do they do this? well when you put a spirit in a charred barrel it absorbs the flavors and sugars from the oak.
we can do this our selves without a barrel by using oak chips / sticks which you can buy from wine making stores or eBay.
all we need to do is toast the sticks first this will caramelize the sugars in the wood, now the flavor you get from it depends on the temp in which you toast the wood. have a look at the diagram that I got from http://www.worldcooperage.com
I'm going to use this for my spiced rum which needs the vanilla flavors, so I need to toast my sticks at about 400 degrees F which is about 204 degrees C so I preheat my oven to that temp.
Now while that's heating up I wrap up the sticks in foil and once the oven is hot enough I pop them in the middle of the oven. I checked it after 1 hour and it didn't really seem very toasted but i did get a burst of vanilla when I opened the packet, I left them in for another hour and then took them out and they looked nicely toasted.
Now I don't know what flavor is going to be best, toasted or charred so as an experiment I weighed and divided the sticks and then using a blow torch on low I charred up half of the sticks, char them do not burn them, remove the blow torch after a few seconds and blow out any flames, once you have charred one side turn them over., I put the charred in one bottle and the toasted in the other bottle with 1L of 60% ABV Rum.
you don't want to age Rum or any other spirit at a higher ABV than that otherwise it could spoil the taste, if your spirit is higher than this then water it down.
I mark up the 2 bottles with dates as well and I will leave them for about 1 month which should be enough time for them to pick up the flavors, also its important to shake them often, every day if possible.
and thats it really once I have the flavor I want I would just strain out the chips and put it through a coffee filter for the small pieces and its done.