This isn't a step-by-step tutorial or a pattern, but a basis to get started with. I don't have any of the pictures of ski masks I've made, but the next one I make I will take pictures of it and add them in here.
For this, you can use any loom and yarn you want that will work with your measurements.
First: Make a gauge swatch with the yarn, loom (start with the loom you would use to make a hat for the size/person you are making the ski mask for) and stitch that you want to make the ski mask with. If you aren't familiar with doing a gauge swatch, don't worry it is simple. Cast on and knit with your choice of cast on and stitch and just make a square-ish piece that is at least 4 to 5 inches wide and square. For most looms you can safely use 20 to 30 pegs and do about 20 to 30 rows, then bind off, but do not tie off or cut your yarn.... Once you take your measurements you can re-use the yarn from your swatch if you want.
When you have the swatch off the loom, pull on it to stretch it from side to side and top to bottom, pull both ways a few times, then lay it aside and let it just rest for about an hour (sometimes when I am in a hurry I don't let mine rest if I'm sure I've gotten it all pulled and shaped to get an accurate measurement). When you are happy with the way the stitches are looking and laying measure how many stitches you get per inch in both directions.
(Note: I keep a running spreadsheet each time I make a swatch with a new yarn. I record the loom, the yarn and exact stitch used then I can refer back to that next time I'm using the same loom, yarn and stitch rather than making a new swatch every time.)
Second: Take measurements so you know what size your ski mask needs to be. Write these measurements down on your notes as you go.
* Measure the widest part of the head around.
* Measure from the bottom of the neck up to where you want the eye opening to start. (*Note: do not just measure the straight line distance, account for the curve up and around the chin as well.)
* Measure from the bottom of where you want the eye opening to be to the top of where you want the eye opening to be.
* Measure how wide you want the eye opening to be from side to side
* Measure from the top of the eye opening to the top of the head. (*Note: this measurement is usually about the same as the length of a regular beanie hat that fits snug to the head.)
Third: Now that you have your measurements and know what your gauge is with your swatch you can begin your designing. Write these down as you go.
* Start by figuring out how many pegs you will need to work in the round on the loom of your choosing. So if you came up with 5 stitches per inch and you need the ski mask at it's widest to be 20" you multiply 5 times 20 to get the number of pegs to cast on. (Note: if you come up with a number that you don't have a loom that fits it perfectly, you can generally safely use 1 to 2 more or less pegs and be ok because of the nature of knit fabric when done.)
Stitches Formula: #of stitches per inch X #of inches needed = # of pegs
* Now figure out how many rows you need from the bottom of the neck to the bottom of the eye opening. So if you came up with 8 rows per inch in your swatch and you need 9" then you would need 72 rows for this portion of the ski mask.
Rows Formula: # of rows per inch X # of inches needed = # of rows
* Use the measurement for how wide you want the eye opening to be and the Stitches Formula above to determine how many pegs you need to cast off to work the start of the eye opening.
* Use the measurement from the bottom of the eye opening to the top of the eye opening and use the Rows Formula above to figure how many rows you are going to work to leave the eye opening.
* Use the measurement from the top of the eye opening to the top of the head and the Rows Formula to figure how many rows to finish up the ski mask.
Now you have 5 measurements and 5 different sections of how many pegs or rows you need for each section. Write out your pattern in a way you can remember and understand what you need to do.
For example: (do NOT use these numbers they will give you something crazy looking!!!)
*Cast on 100 pegs using crochet cast on in the round
*K1, P1 ribbing for 10 rows then knit 62 rounds
*Cast off first 25 pegs and knit the rest of the row and begin working a flat panel back and forth on the remaining 75 pegs for 15 rows (16 rows total for eye opening)
*Cast those 25 pegs back on and knit the rest of that round, then knit 48 more rounds (49 rows total until bind off starts)
*Bind Off using Flat Drawstring Bind Off
And, FINALLY you are ready to make and complete your very own self-designed ski mask :)
I hope this helps anyone that stumbles across it! If you have any questions or comments feel free to leave them on this post, I will try to help out as much as I can!!