A dense film of a conventional surfactant is quite impermeable. On the other hand, a dense film of Janus grains always has some interstices between the grains, and allows for chemical exchange between the two sides; "the skin can breathe". This may possibly be of some practical interest.
Janus am I; oldest of potentates! Forward I look and backward and below I count as god of avenues and gates The years that through my portals come and go. I block the roads and drift the fields with snow, I chase the wild-fowl from the frozen fen; My frosts congeal the rivers in their flow, My fires light up the hearths and hearts of men.
Now, by two-headed Janus, Nature hath fram'd strange fellows in her time.
The very Janus of poets; he wears almost everywhere twofaces; and you havescarcebeguntoadmirethe one, ere you despise the other.john dryden
From mighty wrongs to petty perfidy Have I not seen what human things could do? From the loud roar of foaming calumny 180 To the small whisper of the asp paltry few, And subtler venom of the reptile crew, The Janus glance of whose significant eye, Learning to lie with silence, would seem true, And without utterance, save the shrug or sigh, Deal round to happy fools its speechless obloquy.Rochdale
The sportive hopes that used to chase their shifting shadows on,Like children playing in the sun, are gone—for ever gone;And on a careless, sullen peace, my double-fronted mind,Like Janus, when his gates are shut, looks forward and behind.Apollo placed his harp, of old, awhile upon a stone,Which has resounded since, when struck, a breaking harp string's tone;And thus my heart, though wholly now from early softness free,If touch'd, will yield the music yet, it first received of thee.edward coote pinkney