Here is how I make hand-wax, reposted from my blog, which is aimed more at the beginning amateur medieval reenactment shoemaker than professionals but here it is. Everything I know about hand wax I learned on this forum so if you're new to this read back through this topic for recipies that people use.
I use a basic 2:1 mixture, by weight, of pine rosin and clean yellow beeswax. This produces a wax that works for me, at the temperatures I work in, with the batch of rosin and wax I have at the moment. You will almost certainly need to tune the mixture to suit your own environment and ingredients. I'm pretty sure the batch I made before was 1:1 rosin and wax, but I was using different wax for that batch and it came out way too soft in that ratio with the wax I have now. You will most likely need to experiment to find the exact recipe that works for you.
As you experiment keep careful written track of the quantities and ratios of the ingredients, and keep your finished experimental wax in labelled baggies. If you do this you'll be able to re-melt failed experimental tries and know what you're starting with and what new ratios adding X amount of rosin or wax will result in. It also means that when you find a recipe that works, you can repeat it when you need more or if you are working with different ingredients you have a starting point that should produce something approximately right.
Before you use a new batch of wax on a shoe, build some seams in scrap pieces of leather and see how it works. This will save you building a bad seam in a project you're trying to finish.
The ambient temperature you work at is important. You need a harder wax in summer and a slightly softer one in winter. If you live somewhere with particularly hot summers you may well find that you can't work in summer unless you have air conditioning. Past a certain temperature, the wax just won't set enough to do it's job. Bristles will pull off and stitches won't lock. The only thing to do at that point is to stop working until it's cooler.
When the wax is at room temperature and hasn't been handled it should be hard. I've found that if it is at all malleable at this point then it is most likely too soft to reliably hold a bristle on the thread. Warmed in the hand it should become tacky but never goopy. It's a little harder to tell when it's too hard, but if you wax up a thread and it sheds 'dandruff' during sewing or when a thread that has been waxed and left to set sheds where it is flexed then it's too brittle.
Wax is supposed to be sticky, it is not a lubricant like plain beeswax is. As well as holding the bristle on the thread the wax melts slightly as it is dragged through a stitch and then sets again. The stickiness locks the stitches together in the stitch hole and contributes a significant amount of strength to the seam. I have cut the external parts of stitches off and still had to use pliers to pull the pieces of leather apart because they were held together with little pegs of waxed thread. This also stops the stitch you have just made from becoming loose when you release the tension on the thread. A good test of a wax is if you pull both threads part way through a stitch and leave them to sit for 20 seconds it should take a good hard yank to get them moving again after the wax has set them together.
Anyway, on to the making. This process involved mucking about with very hot melted stuff that will stick to you like napalm and cause nasty burns. Don't spill it on yourself m'kay?
Start with your ingredients. Rosin can be found in various places but it can take a bit of hunting to find a good supply. That stuff came from an antiques restoration supply place in Brisbane (thanks Dave!) called Goods and Chattels. Mistress M found a supply in NZ from a surf wax company of all places. Smaller quantities can be found at arts supply stores but expect to pay about 10x the price per gram there as you would buying it elsewhere. Beeswax you get from apiarists.
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Rosin on the left, beeswax on the right. The rosin is in a mortar because crushing it to a powder makes it melt much faster. It also makes it easy to weigh out exact amounts.
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Crushed Rosin. It pays to hold your hand over the top of the mortar and have some newspaper spread out as chips of rosin tend to go flying when you're breaking up the bigger lumps.
Before you start melting anything get a bucket and fill it mostly full of lukewarm water. You'll need this later, even if you don't set yourself on fire.
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Weigh out your ingredients. Be reasonably accurate with this and remember to zero your scales after you've put your container on before you fill it with the material. Yes, I've made that mistake.
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I wonder how many points(TM) 70g of beeswax is? I ended up using 60g of wax and 60g of rosin in this round, and it was way too soft so I had to go back and redo it. The other problem is that 120g of ingredients is about twice as much as it's easy to taffy-pull (see below) so if you're just making it for yourself, do 60g total. That'll make a lump big enough for several pairs of shoes. If you need to do a big batch pour a part of it at a time when the time comes.
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I use a big tin can to melt stuff in. I've pinched a spout into this one. If you use a saucepan be prepared to never use it for anything else because you won't get the wax residue off the inside. If you do use a tin can, make sure it doesn't have a plastic coating on the inside, or scrub it off if it does, otherwise you'll get melted flakes of plastic in your wax, and that's not good eats.
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Start by melting the rosin. I'm holding the tin can in a pot of boiling water with pot holder used on camping pots. You can do this over direct heat, but you need to be careful. Both ingredients are somewhat volatile when heated and highly flammable. I did the initial melt of the rosin directly over the element on low because the boiling water wasn't quite hot enough to get it really liquid but once it was melted I went back to the double boiler arrangement. An actual double boiler or a mini crock pot would be ideal for this.
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Once the rosin is all melted, add the beeswax. Rosin has a higher melting point that beeswax so it's easier to melt the wax into the rosin than to try melting the rosin into the wax.
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When everything is melted together properly it should be a clear amber color and you should be able to see the bottom of the tin. Ignore the white blobs in this, the bottom of the tin was plastic coated...
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Once you have melted everything together, pour it into the bucket of warm water. I've found that if the water is too cold, like cold tap water in winter, you'll get hard bits forming too quickly. I've had reports from others that they needed to use quite warm water to stop hard bits of rosin condensing out when they poured.
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Keeping your hands under water grab the lump, squish it together and pull it apart. You need to do this under water because the core of the lump will still be liquid and very, very hot. Repeat until there aren't any more searingly hot liquid bits then pull it out of the water.
A note about the following sequence of pictures; I'm doing this with about twice as much wax as I should be and the wax didn't come out very well because of that. A lump much bigger than a golf ball is too hard to manipulate thoroughly. You need to be able to squish the wax around in your hand to keep it soft while you go through this process.
Grab your lump of still-soft wax...
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and pull...
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smoosh it back together...
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and repeat
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This process is called "taffy-pulling", which apparently makes sense if you're familiar with the manufacture of traditional American confectionery. It is critical to the final product. A lot of the mixing of ingredients happens here and without this step the wax will have strata of wax and rosin that aren't fully combined. When you're done with this the whole ball should be a uniform pale yellow. The wax will take quite a long time to fully cool. Leave it overnight before you use it.
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The balls of wax resulting from this exercise. Note marbled color. This wax isn't fully combined because I was working with too much when I taffy-pulled it. I have since re melted one of these balls and added more rosin and it came out much better the second time around. I don't have pictures of that though, sorry.
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You can store surplus wax in airtight baggies. That way it won't stick to anything if it accidentally gets a bit warm. I've heard people say you should store it in water to stop it drying out. I'm not sure how necessary that is but I have found that it is more usable 24 hours or so after making than it is right after it has cooled.