Interleaving Paper for Drawings

It’s time for a resupply to my interleaving paper used to protect drawings and I have a question regarding available products. 

The primary – and most demanding – use scenario I routinely face is for protecting drawings in a spiral bound drawing pad (often Strathmore 400 series paper but not exclusively) from rubbing against the verso side of the preceding sheet. 
These sketch pads are daily carry, get used/opened/consulted frequently, I typically leave the drawings bound in the pad in perpetuity, and they aren’t exactly babied even though I try not to completely abuse them … still pads are often stacked on top of one another – and with books, are squeezed into a backpack jammed with other stuff, are tossed about, etc. which is to say the drawings have a life where the interleaving paper matters a great deal. The most common media for these drawings is graphite but charcoal is also common. With the graphite at times the technique requires very fine detail at a tiny scale and the slightest variation of line thickness and sharpness is a major component to the visual effect, so that even slight smearing to precise lines can degrade the impact and effect of the image. Often these drawings will end up loosing their freshness and crispness. For quite some time I’ve rarely used fixatif (not sure how wise that is) as often I’ll revisit and rework the drawings well into the future. 

The secondary usage is for individual drawings in flat files which in my experience is less critical regarding smearing but still requires archival qualities. 
I use glassine paper cut from a roll. Often after some months graphite will transfer onto the glassine and the drawings can smear a little. For example in a drawing pad that’s seen heavy use and handling if I remove a glassine interleaving sheet and hold it up to the light there will be graphite transferred onto it, enough to make it appear dirty and contaminated. 
At times I’ve taped the top edge of the interleaving sheet to the the sheet of drawing paper (while still bound in the pad) with the belief that it maintains the position of the interleaving paper in a more fixed relationship to the drawing and helps prevent some shifting back and forth and resultant rubbing. 
Many years ago I purchased a drawing pad at New York Central that had interleaving paper built into to it between each sheet … this interleaving paper was white, opaque, and was semi-gloss/gloss (I cannot recall the brand abut IIRC it was a New York Central branded pad but made using a using a quality known paper – and may have been a pastel paper) . I don’t recall ever experiencing any media transfer to that interleaving paper. Any idea what that white interleaving paper may have been? It was extremely smooth … which makes me think that glassine actually has a degree of texture. 
Unless anyone has any suggestions or comments, I’ll likely just buy another glassine roll.
Thanks a bunch.