https://youtu.be/AyDFSqWHw9w?t=7m37s
https://permies.com/t/55045/Medieval-windows-horns
https://en.wikipedia.org/wiki/Alum
https://en.wikipedia.org/wiki/Potassium_alum
Solidified resin from which the volatile terpene components have been removed by distillation is known as rosin. Typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odorous or having only a slight turpentine odor and taste. Rosin is insoluble in water, mostly soluble in alcohol, essential oils, ether and hot fatty oils, and softens and melts under the influence of heat, and burns with a bright but smoky flame.
https://en.wikipedia.org/wiki/Resin
Horn
http://www.personal.utulsa.edu/~marc-carlson/horn/horng.html
Biological Gels as Glazing
I stumbled across one final, interesting option for the original question about materials.
I was looking for "isinglass" (which is a word used for two different things: fish swim-bladder gelatin, and sheet mica). turns out they did not apparently make biological translucent curtains for carriages (not that I've seen, anyway). that was sheet mica.
But translucent gelatines have been used to repair parchment, sometimes with the addition of natural sugars/syrups for consistency; and for preserving eggs (like water-glass, or sodium silicate). Presumably, you could paint gelatine or waterglass over very fine, stretched white fabric, such as muslin, or use it to make "oil-cloth" analogs using thin parchment, or to reinforce something stitched out of the original fish-skin or swim-bladder or animal-hide translucent materials. Seaweed, aloe, or other clear botanical gels could be used in a similar way. Rabbit-skin glue is the traditional 'sizing' for canvas, to prepare it for painting; skin and bone glues, if carefully made and refined, are a smellier version of something that functionally resembles Elmer's white glue (now made with polyvinyl alchol). Bone and hide glues often must be heated, like horn, and can be more waterproof than the other gels I mentioned once cooled.
The other biological-gel materials would likely not tolerate damp conditions well (being similar to agar used for petrie-dish experiments), but are used in dry conditions for paints, plasters, etc. For indoor art work (under wide eaves in dry walls, for example) they might raise some fun possibilities. Other paint and plaster media that I know of include a translucent milk-protein gel (milk plus an alkali like lime; borax is used for "borax glass" and could remain clearer than lime after painting). Egg protein, both yolk and white (the white dries clearer, the yolk is a better suspension emulsifier for pigments, and has more oil).
https://permies.com/t/55045/Medieval-windows-horns
Viking Age
800–1050
Most vikings lived on farmsteads, which were often fenced in. The farmstead was built around the dwelling house – the longhouse – which was also the centre of the farmstead. Various other buildings and functional areas could be present; these might include outhouses, sheds, stables and workshops.
Viking houses were built with wood. The longhouse's bowed walls gave them a ship-like ground plan. The walls were wattle and daub or constructed with wooden planks placed vertically in the ground, which supported the roof together with two rows of posts on the house's interior. Sloping posts were sometimes used for support on the house's exterior. The roofs were slanted and could be thatched or wooden, and sometimes wooden shingles were used.
There was an oblong hearth where food was made – called the long hearth – in the centre of the house. Along the longhouse's walls were benches where the vikings sat and slept. If there were no separate stables on the farm, animals were heId on one end of the house.
Viking Age windows
Viking Age houses had no chimneys; instead, smoke from the fire escaped through an opening in the roof called a smoke hole, or an opening in the house's gable called an owl hole. The smoke hole in the roof also allowed daylight to enter the house, and it was also called the wind eye, or vindauga in Old Norse: ’vind’ meaning ceiling, and ’auga’ meaning eye. Over the course of the Viking Age, the wind eye became a wooden frame over which a translucent intestinal membrane had been stretched, and it began to wander down the roof, probably to allow more daylight to enter the rooms. Evidence of the first apertures in vertical façades is from 870, from an excavated house in Hedeby. It was probably also covered with an intestinal membrane.
When Danes conquered large areas of England in the Viking Age, they left their mark on the building traditions there; thus, the Old Norse word ’vindauga’ entered the English language, eventually becoming the ’window’ that we know today.
The first wooden stave churches were built in the Viking Age. They probably had windows with coloured and painted glass panes, as glass panes and lead glazing bars were introduced.
http://en.villumwindowcollection.com/history-of-the-window/
