Making Mistakes So You Don't Have To: On Using Liquid Mask

I bought this product on impulse, barely even knowing what it was for. I mean, I knew from the name, but I didn't know such a thing existed so it was hard for me to imagine how it was used. Well, falling back on ultimate wisdom and immaculate technique, obviously the thing to do was jump in without tests and use it on a model I put hours and hours of work into converting =D Okay, maybe that wasn't so wise hehe. It did turn out fine, but more experience or research might have prepared me for some of this substance's unique characteristics. This is to be the first of many tutorials/reviews/articles where I try to help you avoid the mistakes I've made myself.

Like the bottle says, Liquid Mask is a resin. Having not looked up anything whatsoever about liquid resin, I had no idea what it would be like once I dropped some onto my palette. I dropped out a generous amount, maybe 7-10 drops and went to apply it with a generic crappy brush I got at a 100 yen shop. I don't even know if I got my brush onto my Wave Serpent's LEDs (no pics really, except in the background of the one up top) before the bristles were ruined. NEVER use a good brush with this stuff. I was damn close to using my favorite (a Loeb sable, best I've ever used) but thought better of it just in time. The Liquid Mask starts to congeal almost immediately when exposed to the air. It becomes a lot like rubber cement. This had my brush gunked up, but I spread the bristles wide and was able to use it like a tiny rubber spatula.

When I did the LEDs I had no real idea how much I needed to apply. As with any mask, all you need to do is cover the thing being masked. The thickness doesn't really matter. But I didn't know anything about this stuff's adhesion or durability. Worried that it might scratch off in handling, I applied a decently thick coat. This caused trouble when it pooled at the bottom of the LED, where it contacts the Serpent hull. Okay, I thought, no problem. I'll just scratch it off there when it dries. Yeah...no. When it dries it gets so rubbery that it is almost impossible to cut without tearing or peeling what you need to remain. I feel like preventing it from pooling in the first place is the best option, but I haven't gotten a chance to try that out.

Here you can see some canopies I did. The one on the left has already been peeled and the one on the right has paint covering the resin. In the picture below you can see from the clear bottom what the resin looks like when dried. Peeling is easy enough. I do it with a tooth pick. Incidentally, I also applied these with toothpicks. But as with the brush they get gunked up quickly and need to be replaced because they stop sliding across the plastic.

Next time I do canopies this way I am going to remember to coat the bottom side too. I spray my primer and these windows look a little foggy because they weren't masked on the bottom side. Although on second thought, since the bottom doesn't need to be done precisely at all and because it curves gradually, tape would work just as well.

Because of the way the resin pools in crevices, I found that I had to go back and black line these anyway. I was hoping doing this would save me from having to be careful when painting around the clear plastic, but it couldn't be avoided this time around. I'd like to try again, redoing parts that pool up too much. If you try this stuff, don't worry about it if you redo parts. It peels easy and leaves no residue. It doesn't rework well at all, so try to get it right while it's still wet.

How would I rate this product after a couple small projects? Only above average considering what a pain in the butt it is to apply. If I could cut it with a hobby knife to clean it up I'd love the stuff, but as is I only like it. The simple fact is that it does something you can't do with tape: mask shapes with steep curvature. It was amazing on my LEDs where I had to spray the hull, but on small canopies that I was painting by brush, I don't know that it saved me any time at all. If you paint with an airbrush it may hold some value to you. On the other hand, Vallejo products are so cheap that it's easy to think "well, I'd rather have it than not...just in case." Dangerous thinking. That's how I've come to have a paint collection that's almost bigger than my model collection.

Have you used any products like this? Were they anything like this one? How well did they work for you?

Zen and the Art of Airbrush Maintenance: Oh you, O-rings!

Iwata HP-BH. Excellent for the scale of our hobby,
though I sometimes wish for a bigger color cup.

I want to talk about o-rings. They are very important to the operation of airbrushes. Simply put, o-rings are there to make a seal. They block air and/or fluids from flowing between parts at a joint. Unlike the stainless steel parts of your airbrush, they do not hold up well when exposed to organic solvents and other cleaning agents. Being made out of rubber, under the wrong conditions they can corrode or maybe swell.

Luckily for me I haven't had any problems like these (yet). The problem I had recently was pretty simple, but figuring that out took a good deal Googling and reading. Basically, the trigger was sticking which meant air was continually flowing through the valve. There are a two most likely causes for this. One could be that the o-ring is swollen and squeezing the piston. That could prevent the control spring from returning the button to the off position.

In the image above, the control spring is inside that detached piece, which is the air valve set. Air flows through this when the piston, visible as a silver circle in that hole just below my index finger, compresses the pin at the top of the valve set. The piston o-ring is barely visible around the piston there.

Disassembled airbrush with the top of the piston visible through the trigger slot.

The other cause, the one that I had trouble with, is that the o-ring could need lubricant. If there is too much friction between the piston and the o-ring, it could cause the same problem as the situation I described above.

Here you can see the o-ring and the piston separately.

From what I have read, you have to be incredibly sparing in how much you apply. Using too much could result in getting oil all throughout the air passages. That could contaminate your work later on when you spray. I used a toothpick and a really tiny kind of Q-tip I buy from a local hobby shop. Apparently you also need to avoid some oils that can damage the rubber. Iwata has a specialty lubricant of their own, but as with most specialty goods I expected my local hardware store would sell a product in some ridiculous quantity I could never use up. Probably 90% cheaper than the brand name one too.

What I found was a huge tube of lithium grease. I wasn't sure that the recommended lubricant, Medea Superlube, was a lithium grease so I had to Google until I found the material safety data sheet (the MSDS). Be sure to look around for yourself if you want to use an off-brand as different companies use o-rings made of different materials.

This post is mostly about the o-ring that was giving me trouble, but there is another important o-ring in my model (probably in all of them, I'd think) and it is the one that creates a seal around the needle. I couldn't get a picture of it, but it is just behind the color cup. That one also needs to be lubricated as you don't want friction between it and the needle. I wasn't having any problems with that one, but I went ahead and greased it anyway while I was at it.

When I finished, I sprayed two shades of purple over the course of an afternoon and didn't have any more issues with the trigger. I'll post more about these sorts of topics, but it'll be most likely if I have a problem with some of my hardware. Let's hope that's not the case!