Buckram is a cloth material used for stiffening clothes or covering books. However it is now commonly used in creature costumes for eyes because it has even, tiny holes all over its surface making it see-through. There is a wide list of materials to use for eyes, but buckram is easily one of the most popular choices. Buckram is easy to color and has a lot more holes per square inch that are smaller than a similar material called aida cloth (used for cross-stitching). Perforated plastic works too though it will need to be primed in order to paint. Window film or sunglasses have been used for eyes but they tend to fog up; perforated materials allow more airflow. I have also seen interfacing and chiffon used with varying results.
Buckram can be colored with markers, painted, dyed, and even printed on. In general, you need to avoid contact with water as the colors will run. If you ever wash your suit head by fully submerging it in water, you need to remove the eyes first.
The rule of thumb is that white is the hardest to see through and black is the easiest to see through. It works so well for eyes because it filters light- it will appear more solid to the audience since the light is being reflected back to the viewer, but for the wearer who is viewing it from a dark environment sees through it like a window because their eyes are right up against it looking into a lighter environment. Many people ask what is it like to wear a suit head and to see, so because it filters light, it's comparable to looking through a foggy pair of sunglasses.
It can be purchased at fabric stores or online, also available at FursuitSupplies.com. JoAnn Fabric and Craft Stores carries it in the utility fabrics section under the name "Unicorn Buckram" (which is the product demonstrated in the GIF). It also comes in various weaves and both have a trade-off: looser weaves are much easier to see through, but because the holes are bigger they are more noticeable. Tighter weaves are harder to see through but the holes are less obvious. Often it is more important that you can see properly because it is safer, so use a tighter weave at your own risk.
Eyes can be made entirely of buckram, though the holes will be much more obvious, the benefit is that you can see through the entire eye:
Or what is much more common is a combination of smooth, shiny plastic to act as the sclera (whites of the eyes) with a hole cut from it for the pupil/iris to be made from buckram, but you will have a smaller vision hole:
Even though buckram is stiff, it is still recommended that you make a plastic frame to stretch the cloth over to keep it taught. The plastic for eyes is most commonly cut from a cheap bowl or a thin plastic (styrene) sheet. I have also seen foamies used for the sclera (or eyeshines) but they won't give you the support like plastic will. The advantage of buckram is that you can see through both the pupil and the iris because you can color them how you wish, but alternatively you can paint the plastic around the buckram pupil to be the iris color. In this case you don't necessarily need to use buckram as there are many other see-through materials that are solid black. Here is an example:
Tutorial and close up images here: www.matrices.net/eyes.asp
If the sclera of your eye is not present (or is a different color other than white) and you don't want to use buckram on the entire eye, you can get this effect by painting the plastic a color or finding it pre-colored: This eye does not have buckram for the pupil, it is plastic canvas but same principal
If there are any more questions about it, feel free to ask below and I will help you out or add it to the description here!
Ideas for eye shapes/styles:
Tutorial for making buckram eyes:
Eyes made with plastic canvas:
Honnestly, I couldn't find buckram like that.
The one I got was entirely different...
Also, how do you color the buckram? What would YOU support? 'Cause I just can't get it to work.
I go through a great deal of hassle to seal buckram eyes, I haven't found a sealant that I'm totally satisfied with, but the whole process is touch and go. I even sealed the painted foamies, mostly to keep them from running, but how well it will hold up to hot days and sunlight remains to be seen.
I always value a tutorial, even if I'm set with a method, I still want to see if there's anything new that can help. But I am still struggling to handpaws. oh my sorrow
If you find something that works, I'd be happy to check it out. At one point I was so frustrated with the running effects of gloss sprays I used, I had thought of trying mod podge paint on, but that would be similar to laminate and like you said the airflow is so important, plus vision would be null. I think what I've been using was a mod podge (spellfail) gloss spray, that had the least amount of running if I sprayed gently after each use of the colored markers. But you can't alter the colors once they've been treated, being waterproof and all
I think any sort of waterproof acrylic spray does the job if done right, but like I said it can be hit or miss, the colors have a tendency to run if the material's left slanted, or clumps. But once they're treated the threat of sweat ruining them is null. I've seen a few tutorials where builders have mentioned treating the eyes, but I've never asked what they use.
Good luck, I hope you find something that implements all the advantages of waterproof eyes. I hate spending an hour or something with the colors only to have it ruined with the running mess.