Ramdadan Kareem Everyone, I am about to embark on making some attars for personal use. My plan is to make small amount say 4-5 grams in borosilicate vials (not those high recovery ones) and let them sit there for while to age and then transfer them into typical study glass vials 2.5 grams. I was wondering if should I use PP screw caps with TFE (aka PTFE) lining or HDPE screw caps with integrated ‘plug seal’. If possible, I also want to reuse these bottles and caps. I imagine different oils react differently to those type cap materials. But hopefully nothing serious as none of them will be too much in the mukhllats, except ambergris, ouds and white florals. Just in case I need to be aware of any oils, here is a note list of a tentative one. Top: elemi, bergamot, Zanthoxylum, clary sage abs., lavender abs Middle: Taif Rose Otto, Turkish Rose (Otto and Absolute), Musk Rose, J. sambac (abs and EO), Tuberose abs, Gardenia abs, Egyptian Jasmine abs., Lily of the valley Base: Labdanum, Oud (wild Assam, Cambodia, organic Bangladeshi, and org. Thai), Civet, castoreum, grey ambergris, fir balsam, tobacco, hay (abs and EO), hopefully saffron, myrrh, frankincense, Mysore sandalwood, tobacco abs, and birch tar. I would be grateful if you can let me know what type of screw cap I should use – PP with PTFE lining or HDPE with integrated plug seal. Thank you for reading my long post!