Of course, I'll give you more info about it.
That's a 70/30 (80ml of base, 100ml of capacity) base + 10Ml of Aroma + 5ml of nic 1,5. Mixed them make an e-liquid like the other one that everyone make.
It's strange, because I've always used to make e-liquid with these concentration.
Okay; so what I am understanding you to say is, that your recipe is:
84.21% 70
PG/30
VG base (80mL)
10.53%
Big Mouth brand, Beast - Melon Kick flavor concentrate/aroma (10mL)
5.26%
1,5 BlendFeel nicotine (25mg/mL nic concentration in a base of water) (5mL)
If all that is correct; this is your result:
With that understanding; I see two potential causes for a harsh vape:
1.) High ratio of PG. PG is known to "add" throat-hit (harshness) to vapor. To rule this out, if you have any of your PG/VG base left over, try vaping a little bit of it. Without any nicotine, or aroma, you will be able to quickly notice if this has the same/similar harshness.
2.) Higher than recommended amount of flavoring:
(Note: this was taken from Big Mouth's DIY(mixing) instructions found on product's web-page. See above link)
10.53% verses 8% is not totally out of line; but it is high. This really comes down to a matter of personal preference/taste. Some individuals have very sensitive taste buds, and require less flavoring. While others have insensitive/damaged taste buds, and require more flavoring. So, how much any one person requires, is a matter of trial and error. If you have leftover PG/VG base, you could take a
small amount of your completed recipe, and add a little more of your base to it to see if a lower flavor percentage helps.
This is also why the manufacturer recommends:
Additionally, I see the description of the aroma is:
Sour is often accomplished by using Malic Acid, Citric Acid, or a combination of both. These mild food grade acids
can be (more or less; depending on the individual) somewhat irritating. An additive like Ethyl Maltol, or Sweetener (Sucralose) can help to mute the harshness and add a bit of sweet. If you don't want any added sweetness; you could use something like The Flavor Apprentice (TFA) product named Smooth:
One final thought: it may also just be a matter of time. Some liquids/recipes just require time to blend, mature, and sometimes soften. This is why the instructions also say:
Time also can allow Ethanol to evaporate. Ethanol is sometimes used as a flavor carrier, and is found by many, to add a noticeable harshness. If the Ethanol content is significant, it's evaporation can be accelerated, by leaving your mixture sit with the bottle completely uncapped (both cap, and dripper top removed). Just don't go overboard with the cap off, as this can also permit flavor loss (especially with some citrus flavors).
Sorry that this post is so long; I hope you find something useful in it. Let us know how you progress.