Start by weighing your Ingredients. Place oil and emulsifying wax in one saucepan. Then place water, glycerin and keratin in a second saucepan. (To make it easy, I place a saucepan on the scale and zero out the reading. Then measure the ingredients, zero-ing out the reading between each.)
Heat on stove until both containers come to 158°F. Turn the heat to the lowest setting and continue to heat for an additional 15 minutes. Make sure the ingredients remain around 158°F.
Turn off the heat. Then add approximately 1 ounce of water to the water/glycerin mixture to replace the water lost through evaporation.
Combine the two mixtures and mix with an electric mixer for about 5 minutes.
Let the mixture continue to cool for 15 minutes or it's cool enough to touch (but still warm). Add essential oils, collagen and preservative. Mix well.
Divide among several small bottles or one larger bottle. Allow to cool overnight.
Notes
Even with an emulsifier, your mask may start to separate after a while. Shake before each use.