The official liquitex website to find out more about this product can be found [HERE]! Note: There IS a "tl;dr" at the end so feel free to just scroll down until the end.*AHEM* Anyway, I happened to come across this new product in my local art store:
It comes in 3 different kinds: Satin, Matte, and Gloss. I chose to test out the 'Matte' because I didn't really fancy having a shiny dollieh face.
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This is a close-up of the label:
"Water-based"? "Contains UV protection"? Ooh, sounds promising. And although it doesn't say so on this label or the liquitex website, the website for the art store I went to said that it's non-toxic. I just had to try it out. By the way, I spent around $15 for this. It does say "non-removable" and "permanent" but... Eeeh, that's why I decided to test it first.
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Now obviously I wouldn't want to ruin my poor dolls with a new product like this. Therefore, I took Neil's headcap and decided to test it there instead. This is how it looks when the spray is still wet:
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After about 10~15 minutes, it becomes completely dry. It's VERY easy to tell because it becomes like this:
You can no longer see my ceiling lights get reflected off of Neil's bald head.
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I put on 3 coats (since that's the amount I plan on putting on before doing any face-ups) and applied some "dollieh make-up" on top.
What I wanted to test here: 1. How well pastel would apply on top of the coat. 2. That the coat won't scratch off from drawing with watercolor pencils.
Result: 1. Pastel works really well on this! The pigments stick right on it and comes out clearly. 2. Didn't scratch from the watercolor pencil, yay!
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I applied a final coat on top and waited for it to dry. As you can see, I decided to test out one more shade of acrylic paint.
Now I conducted another important test: leaving the headcap under running water. Why? Obviously I want to be able to touch and/or wash my doll without having to re-do a face-up every time I did a bit of maintenance. This is how it looked AFTER I put the headcap under running water (FULL POWER! 
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None of the "face-up" came off at all!~*~
Now the final and most important test (at least for me): Can I remove it? The answer is: YES!
Just so you know, I've never used MSC before myself so I don't know how hard it is to take that off, but I can say this: cleaning this headcap was effortless. I used the "Winsor & Newton Brush Cleaner", and the entire thing just came off with barely any effort on my part. As you can see, the headcap is completely spotless and back to normal.
Note: The lighting in my bathroom is different, that's why the headcap looks like a different shade. No dollieh caps were damaged during the photography of this review-like post.
tl;dr
The "Liquitex Professional Spray Varnish" worked like a charm! It's water-based, non-toxic, has UV protection, and is easy to clean and apply. I think this is definitely a nice alternative to the famous Mr. Super Clear (which I cannot find in my region), and I'm going to use this for my first face-up soon.
EDIT2: AAAH! Sorry! In my excitement I didn't realize that I put this in the wrong section! Really sorry, please move it if necessary... T_T ---> Oh, nevermind. Guess it's fine here.
EDIT3: So yarwel has brought the safety sheet to my attention and I've taken a look at it. Basically if I summarize the safety warning, it seems that while the chemicals used to make the product are irritants (not toxic on their own), a by-product (formaldehyde) is present in the spray which is toxic if inhaled or with skin contact. Personal protective equipment is still recommended.
Thank you.
