This could be resin that have oozed out of a wound on a tree, it does not matter if it is old and dry and full of dead ants. the important thing here is to not kill the tree, we need them for more important stuff, like transforming CO2 to oxygen.

Do some mechanical cleaning, try to remove some of them dead ants and most of the bark.

Put the resin in a glass jar and fill just enough alcohol so that all resin is covered in alcohol.

Stir or shake until the resin is completely dissolved. It's ok to leave it overnight if you don't want to stir so much, do not use the oven to heat it up as the liquid and the gases is extremely flammable at this point.

Use a coffee filter or similar and filter the liquid over in a clean glass jar, add more alcohol if you are having problems with the liquid being to viscous to pass trough the filter. Repeat the filtering process if necessary.

Now you can adjust the viscosity to your liking, for a thicker product you just leave the jar without a lid so that the alcohol evaporates, and if you like it thinner just add more alcohol, just remember that by adding alcohol you also thin out the active ingredients, so don't add to much. Some like it being very syrupy so that one can use it to tack down smd components to the pcb. For hot air soldering maybe it's better with a thinner product. Make a little of both and try to see what you like the most.

Now you can solder together your time machine using a more environment friendly flux.