Reddit mentions of Propylene Glycol USP Kosher Certified 100% Pure Food & Pharmaceutical Grade - Highest Possible Purity - 138 oz. nt. wt.

Pretty much. If you've ever looked at them closely, this is what it looks like broken down, which is a lot more than you need to do here but it'll at least help you see the anatomy of it. What you'd do is:

• get the chimney off (the top metal part with the rubber gasket)
  
• pull the wick (the two little loose white threads and the one big one that's threaded through the wire coil) out sideways with tweezers
  
• twist/roll some wicking material (hard to describe exactly how much you should use but you should be able to figure it out with a little trial and error, it's not like you'll have a shortage of cotton/rayon) tightly enough to thread through the coil
  
• thread some through the coil and lay a little more on top, untwisting/unrolling it just a little to expand it
  
• replace the chimney, grab some scissors & trim the coil flush with the widest edge
  
• place coil in tank as normal
  
  That's pretty much it but like I said before I highly recommend rayon wicks for flavor, so much so that I was dead serious when I offered to send you a baggie full for free, it's really that good and if it'll help you kick analogs once and for all it's more than worth it even if you don't pay it forward eventually (though I would ask you do that if/when you're able, the little baggie will last you at least a few months but the $15 box my wife and I have will last us several years even if we give away 3/4 of it).
  
  Also, if you really want to save a lot of money (and possibly get a new hobby lol), look in to making your own ejuice. It's only as difficult as you want it to be, it can be as simple as mixing two ingredients in a bottle^(1), or you can scale up the complexity as much as you like^(2).
  
  Hope this helps!
  
  ^^^^^^^^^.
  ^([1] One quick example, say you really like )^(MBV's Banana Cream Pie)^( and want to keep your nicotine around 9mg/mL, just mix 24mL of )^(12mg base)^( with 6mL of )^(BCP flavor)^( and that's it!
  [2] cheapest way to go is getting )^(100mg/mL nicotine base)^( and get )^(straight VG)^( and )^(PG)^( to dilute it to your desired strength; plenty of recipes on /r/DIY_eJuice to get you started mixing your own concoctions, some with only one or two flavor ingredients some with more than six!)
  

I'll break down a 30ml of my own for some real price examples.

Bottles

dropperbottles.com, 110 bottles for $37.40, $45.40 after taxes and shipping. That comes to $0.41 per 30ml bottle, the most expensive portion.

Labels (because I like to be fancy)

Avery 6879 labels from Amazon, $15.88 for 300 labels, free shipping. Comes to $0.05 per label.

VG

Gallon of Froggy's Fog VG from Amazon, $24.99. $0.007 per ml.

PG

Gallon of Froggy's Fog PG from Amazon, same price. $0.007 per ml.

Nicotine

Liquid Nicotine Wholesalers 100mg Nic, 240mL, $14.99. It was about $19 after shipping. $0.08 per ml.

Flavor-wise, let's go with a simple one. Prices from Bull City Flavors.

/u/ID10-T 's Cranberry Sprite.

• FLV Cranberry 1% (15ml for $5.49, $0.36 per ml)
  
• VT Fizzy Sherbet 2% (30ml for $6.49, $0.21 per ml)
  
• CAP Lemon Lime 3% (30ml for $4.00, $0.13 per ml)
  
  Breakdown of a 30ml bottle of 3mg 60VG/40PG Cranberry Sprite
  
  
• Bottle: $0.41
  
• Label: $0.05
  
• 18 ml of VG: $0.126
  
• 9.3 ml of PG: $0.0651
  
• 0.9 ml of 100mg Nic: $0.072
  
• 0.3 ml of FLV Cranberry: $0.108
  
• 0.6 ml of VT Fizzy Sherbet: $0.126
  
• 0.9 ml of CAP Lemon Lime: $0.117
  
  Total cost: $1.07

I can make enough juice with a 1/4 to last me quite a while, a lot longer than straight herb will last me and I can control the amount in each batch more closely to desired results. If I wanted to I could make some crazy one hitter quitter juice or I can make some slow sipping, you just regulate the amount of VG you use in the process and how much dilution with PG to get desired results.

A gallon of VG is like $19 on Amazon to your door, PG is a little more but this will be enough to last you several batches, probably at least a years worth of juice making. Only other investment is a crock pot, mason jars and maybe a strainer or cheese cloth which is a negligible investment.

Edit VG 35 a gallon (not a promotion just example)

http://www.amazon.com/Vegetable-Glycerin-Food-Grade-Kosher/dp/B000RT9JGK/ref=sr_1_7_a_it?ie=UTF8&qid=1457639437&sr=8-7&keywords=vegetable+glycerine

Food grade PG (same disclaimer)

http://www.amazon.com/Propylene-Glycol-Perfect-Sweetness-Highest/dp/B00GI2CIQS/ref=sr_1_7?ie=UTF8&qid=1457639514&sr=8-7&keywords=propylene+glycol

Propylene Glycol - Food Grade USP - 1 Gallon https://www.amazon.com/dp/B00GI2CIQS/ref=cm_sw_r_cp_api_i_s6QODb5ZSX4RK

Good stuff

I really appreciate you taking the time to give your professional opinion on this. I've been torn with the huge difference in price. I'd ultimately like to get this all controlled by a smart PID microcontroller and I think accuracy on the freeze point/purity will be important at that point.

In terms of purity, how will the documentation compare to a brix reading? I imagine those are two very different factors but it is worth asking.

Secondly, is it true or false that the glycol should be replaced ~yearly? If so, that is definitely tougher to swallow but I'd like to know either way.

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I was originally looking at: https://www.amazon.com/Propylene-Glycol-Food-Grade-Gallon/dp/B00GI2CIQS

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