Calcinator and retort or calcinator/retort only

[Картошка ❄]

I tested a bit, and... Why does my potions turn out having longer duration if i use only calcinator or only retort, and only slightly longer than pestle alone if both? Aren't calcinator and retort supposed to enhance each other's effect, working synergetically? Why are they needed then?

[Картошка ❄]

And yet there are cases when together they give longer duration than if apart... So weird. What can be causing this?

[Nebgama]

if using both Apparatus and its considered a negative effect then it will be reduced much more in duration than if you where just using one Apparatus.

[Картошка ❄]

There was no negative effects...

[Ghost]

Normally it works like the following but some potion effects, invisibility for example, behave weird. There doesn't seem to be a clear reason why.
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Alembic reduces strength and duration of negative effects.

Calcinator increases strength and duration of both positive and negative effects.

Retort increases strength and duration of positive effects.
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When using Calcinator and Retort together the formula changes slightly.

If using Retort or Calcinator, round the RetortQuality or CalcinatorQuality (as applicable) to the nearest whole number (minimum 1) and add it to both base duration and strength.

If using Retort and Calcinator, round both RetortQuality and CalcinatorQuality, then add CalcinatorQuality + (RetortQuality * 2)

[Картошка ❄]

Sounds about right that some effects are just weird. Could it be that purple ones are all weird, like invisibility, feather, telekinesis, etc? Didn't test particularly enough.