unyquity
I've seen a couple of variations on this formula, but never one with grape seed oil. Using grape seed (in part or in whole) for the olive oil could be the culprit.
At one time,
Dr. Schulze s website showed that he used various flower oils, but now it just names the flower (so I don't know what he uses). The original formula from the SYL manual called for the flowers of Calendula, St. Johns & Arnica...so that's what we use. I do not see mustard powder listed on his website (or the SYL manual).
The various *powders' that you've used may have somehow 'soaked up' the oils - we've never experienced that complication/problem. We usually put all the dry ingredients in the jar first, then add the oils, then shake like crazy, and pop it in the dehydrator. The only ground/powdered herb we use is the African Bird Pepper/Habanero combo...and we 'rough grind' those ourself from whole/dried peppers.
Melting the menthol crystals is not going to add a lot more liquid, but when the crystals melt, there will be more liquid (thick).
When we make it, there's ample liquid for shaking/mixing, but the jar is mostly 'herb'. After the menthol has melted & and it's all macerated (and the solids have had a chance to settle at the bottom), the jar has a mixture that is about 35/40% solids and the rest liquid...but it does NOT fill up the gallon jar.
'Hope that gives you what you need :)
Blessings,
Uny