In DIY 101 I outlined the general process of mixing DIY eLiquid, but intentionally left out mixing by weight. While this is the most accurate way to mix eLiquid, it is also a bit more complex than mixing by volume.
In this post I am going to try to cover everything you need to get started mixing by weight.
Mixing by weight requires some specific equipment that mixing by volume does not (though there is some cross over, so don’t worry about having wasted money on equipment if you started mixing by volume).
Digital Balance (scale)
The most important piece of equipment needed to mix by weight is a digital balance (scale). You really don’t want to use just any scale either. A scale for DIY mixing should meet the following requirements:
- Resolution of not less than 0.01 grams.
- Large enough capacity to accommodate the weight of the bottle size and liquid capacity you will be mixing.
- Tare function.
- Relatively quick register of small weight changes.
- NO AUTOMATIC SHUTOFF.
That last one is very important, as if you are in the midst of adding an ingredient and the scale powers off, you will likely need to dump the bottle and start over.
If you can’t find one without auto shutoff (in your price range or whatever), at minimum the auto shutoff (if it is not possible to disable it) should be after more than 5 minutes of inactivity.
The first scale I used had a 60 second inactivity auto shutoff, and after the second or third time I had to dump a mix because it powered off while I was adding an ingredient, I had to replace it.
My recommendation for a starter balance is this guy. There are plenty of other scales out there, many cheaper, but in my opinion this is the best bang for your buck.
No matter the scale you choose, you’re going to need a (possibly a set of) calibration weight (the one I suggested comes with).
These instruments are very sensitive, and it is important that you not drop them or exceed their rated capacity. I don’t even like to get really close to max capacity on a digital scale. The sensors are easily damaged. The scale I suggested is rated for a 500g capacity at 0.01g resolution (often noted as 500g x 0.01g), and I would not place over about 450g on the scale.
When mixing by volume I recommend syringes for dispensing liquids due to their accuracy, but when mixing by weight the scale takes care of accuracy. This makes droppers or pipettes almost a necessity.
Some flavor vendors sell small sizes of flavoring in squeeze bottles which is super convenient when mixing by weight, but others (I’m looking at you WizardLabs) use small glass vials that come without dropper caps.
You could use syringes for this (in fact I do for some things), but that is probably going to slow down your mixing process.
Disposable pipettes are pretty cheap, but you can also get droppers cheaply. As a side note, WizardLabs does sell dropper caps that fit their flavoring vials.
What you use is totally up to you, and what works best for you. I find that dropper bottles are fastest for me, but barring that I like to use recycled droppers:
I’ve got tons of empty bottles laying around. I started keeping the droppers after I broke like 5 bottles while cleaning and figured I’d hang on to the droppers for dropperless bottles. Turns out it was much better for DIY.
If you want absolute accuracy when mixing by weight, you’re going to need to figure out how much everything weighs.
Specific gravity (SG) is the weight of one milliliter of the liquid at a given temperature.
Some vendors (like TFA and Capella’s) thoughtfully provide MSDS links for most of their flavors that list specific gravity.
Generally PG has a specific gravity of 1.04 and VG has a specific gravity of 1.26, or there abouts.Note: Specific gravity of liquids does change as temperatures increase or decrease (temperature changes cause density changes). This is a really small variance and all density changes will be equal at the same temperature, so you can either ignore it or do all of your measuring and mixing at the same temperature.
If a vendor does not list SG, we have to measure it. If you are going to do this, I would recommend measuring as much of the liquid as you can (10ml should be enough to give an accurate measure), and then divide the resulting weight by the number of ml measured to give you a fairly accurate SG for that liquid.
This can be quite a pain, and does waste some flavoring (some is going to stick to the measuring vessel and dispensing utensil).
Alternatively you can just assign a given weight to all of your flavorings. Many people mix by just assigning either the weight of PG to all of their flavors (because the vast majority of flavors are suspended in PG), or just assigning all flavorings a value of 1.
Both methods have their advantages, and I would not necessarily recommend one over the other. It’s all going to come down to what you want to do.
I will note that the primary reason that mixing by weight is the most accurate is that it is fully repeatable. Even assigning a random value to the weight of all of your flavors (I like 9, so all of my flavors will weigh 0.999g!), so long as you ALWAYS use that value, will give this advantage.
Which ever you choose, I would very much suggest that you do one or the other (if for nothing other than your own sanity).
To start mixing by weight, we need to translate our recipes from percentages to weights. I’m not going to even attempt to explain the math used to do this manually, just use a mixing calculator. The one I recommend in DIY101 is still recommended here, but there are many that will do mix by weight.
Once we have a recipe, and everything laid out and ready the process is pretty straight forward:
- Check your scale for accuracy, calibrate if necessary.
- Place your empty bottle on the scale and hit the Tare button on the scale (this will zero out the scale).
- Add your first ingredient (slowly so that the scale has time to catch up with the changes). Once you have the amount called for in your recipe (or close enough, you may be off by 0.01g or so), write down the amount you added of that ingredient.
- Press the Tare button on the scale.
- Repeat the previous two steps until you are out of ingredients.
The first few times you mix by weight are going to take a (relatively) long time as you get used to the process, but once you have it down, and have your mixing station set up correctly you can mix a 30ml bottle of eLiquid in just a minute or two depending on the complexity of the recipe.
Mixing by weight is fast and repeatable. As always, the most important thing is to document what you actually do, so that if you somehow hit on that magical perfect recipe, you can repeat it precisely.