Thursday 14 May 2020

Air Brush Learnings

This tool is a need to have for modelers. I can't imagine not having it and it gets used alot. I got my first airbrush back in 1995. At that time I could already see that if I wanted CNR models they would have to be painted and decaled because back then there were very few proper models that were painted correctly. I started out with a Badger 200 single action, with gravity feed brush that I bought off a friend of mine for $30. I can't say enough good about dealing with Badger especially during the transition to acrylic paint. I then got a really good deal on a Testors Aztek 470 brush that worked ok but it is now hard to get tips for it. It is a double action side feed. I now have a Paasche VL double action side feed which I really like mostly because of the 3 different size needles that it has. It is also easy to clean as airbrushes go. 

Badger 200
Aztek 470
Paasche VL

 We will look at types of air brushes,paint, masking, cleaning, paint mixing, paint booths, air supply, material your painting, practise and some other tips for painting. There is also lots of info on line. The things I am covering here are the ways that I do things from having painted 200+ models. I have also done some custom work but only do charity work for people who need help.

 All brushes have a single trigger. All airbrushes fall into 4 categories of control. These are single and double action, pistol grip and automatic. I have have a single, double and pistol. The single action means you only control the paint flow. The double action means you control the paint and the air. This done by pushing down on the trigger for air and pulling it back to get paint flow so both are variable separately. The pistol grip is on a larger brush I have. I recommend a double action and with a little practise it is easy to do both at the same time and you have the versatility. Most brushes have an adjustable stop on the paint flow so you can't get to much.

There are 3 different types of feed. Gravity, siphon and side feed. Gravity has a paint cup on the top of the brush that holds the paint. The paint flows down with gravity and is mixed with the air and is atomized. With a siphon the paint can be pulled up through a tube from a jar under the brush. With the side feed the cup is mounted on the side of the brush may do both gravity and siphon.  My Badger was a gravity feed, my Testors and Paasche are both side feed. I do not use a bottle very often because there is more to clean. I use the smaller side cups. A nice touch with the Testor was that the cups had caps so the paint will not spill out as you change angles when painting. I have to be mindful of this with the Paasche as I can spill while try to paint at a difficult angle.

  There are 2 different types of mixing which are internal and external. With internal the air and paint is mixed inside the brush before it comes out of the tip. External the paint and air are mixed at the tip. I recommend the internal is old school and most brushes now come as internal. All my brushes are and have been internal. External is also cheaper but just not worth it.
So as a recap I would recommend a double action, side feed with internal mixing.
   Paint falls into 4 categories. Acrylic, lacquer, enamel and oil based. Each of these types of paint require their base used to thin the paint. Acrylic is becoming the most common these days and are the easiest to clean up. These will come up under a few brand names. People refer to it as water based which is not really correct and will make your search harder. Lacquer and enamel are similar in the fact that they are tougher to clean up and you will need to clean your brush with lacquer thinner. The most common enamel that people are used to would be the little bottles of Testors model paint. Nail polish would fall under the lacquer category. I use acrylic about 90% of the time on a multitude of surfaces and never have any problem. The thing that makes some paints better than others is how fine the grind is on their pigments. The finer the better, house paint is coarse, craft paint is next  and then model paints and nail polishes. 

  Painting. The reason why most people, myself included, really like solvent based paints over acrylics is the way they spay and the smoothness of the finish. You can achieve the same result with acrylics by adding some extender to the paint. I add an extender to the bottle of most of my acrylic colours that I want that fine finish. What this does is extend the drying time. The problem with acrylics is they dry fast, so fast that they are drying on the way to the model. The ruff finish is little pieces for paint that have dried on the way so they are ruff.  Too high an air pressure can cause this also being too far back from the model. Some models of brushes have special cones and needles for spraying  acrylics. Oh...before you buy a brush check to make what kind of paint you can use in it.

  There is 3 categories of finish. They are flat, semi gloss and gloss. The main diver in your choice is what type of decals you are going to be applying. You need to understand what your paint type sheen is as it is not always easy to know. If you are not sure, contact the manufacturer and they can tell you. For water slide decals you need gloss or semi gloss. Gloss will allow the decals to snuggle down 100% of the time. Semi gloss may or may not work as well and takes a little more care to get your decals not to glaze or be shiny. For dry transfer decals you want flat as it will work 100% of the time and about 10% of the time with gloss paint. Now to overcome this you can spray your model with a dull coat and then they will work fine. You can also spray your model with gloss to make wet slides work better. Make sure you spray the whole model so the finish is the same all over or you will see it. 
  There are 3 types of clear finish. They are flat, semi gloss and gloss. They can be applied after the model has been painted to get the affect you like. There are the same types as there is paint. 

There are 2 types of masking: they are liquid and tape.Masking is a bit of a personal thing, so these are the things I do. You can buy special masking tape but I use green or blue painters tape, plain tan coloured masking tape or tan coloured drafting tape. If you are masking a none painted surface say on the first coat you can use any of the above tapes. If you are protecting a painted surface use the painting tape or the drafting tape. Drafting tape has the least amount of glue on it as it is designed to be removed from paper. I will lay down a strip of tape on my glass desk top and lift it on and off a couple of time to remove some of the glue. Next I will make a clean cut on the edge of the tape on any edge that needs a crisp line. If you look at the tape under magnification it has a fuzzy edge to it that will show up when you remove it. Also make sure that the paint surface that you are masking has fully cured before putting tape on it. I use the dull side of an Exacto knife or a burnishing tool to get the tape to stick on the edge. The middle part on 1" wide tape doesn't matter, just the edges. It will take you 3 times longer to do a good mask job than it will to apply the paint. When painting an edge do a light coat spraying from behind the edge and let that dry. This will seal the edge then you can paint from any direction and not get bleed. Still try not to paint into an edge. As soon as the paint has cured you can remove the tape. By this I mean do not leave it on longer than you have to. When you remove the tape by getting hold of an end and pull it back  over itself and it will look like  C  this will help in not pulling up the paint that is under it. This trick also works for house painting. There is also liquid tape which can be use to cover odd shaped details or windows that have glass in them. Go slow and take your time to get right to the edge of a window with as clean a line as you can get with a brush. Then paint. Once it is dry you can pull it off with fine point tweezers or the tip of an Exacto knife.

Cleaning your brush. Next to masking this takes the most time and must be done well. Expect that it will take 20 min to do. Lest time to change colours if you are going from light to darker colour. For acrylics I use water and clear windex which has no NH3 (NH3 is bad for some brushes) or if you would like to use a bought product the best I have ever used is made by Iwata and is called Medea AirBrush Cleaner. For any other paints I just use lacquer thinner and flush it with water after. For my Paasche I flush it with water and add water to the cup, rinse it, dump it out a few times, flush with water again and spray it through the brush. I then remove the needle and wipe off what paint is on it. I clean the tip with a toothbrush and then put the needle back in and pull it out cleaning it again. I then run some cleaner down the shaft that the needle travels in. I then slide the needle in again and if it is clean then I tighten it and run some clean water through it. DONE

Mixing paint is only done by stirring as you do not want to introduce air bubbles. It should be the consistency of  milk when it drips off your stick. I only use distilled water to thin acrylic paint and whatever the medium is used for other paints. I have sprayed craft paint but it needs to be cut alot and I use a bigger needle and tip. They do not stick great but if it is going on a model that will really be touched it doesn't matter. Nail polish also needs to be thinned quite a bit.

My paint booth. The booth shell cost me about $10 to make. The ($100 at Acklands) fan is a centrifugal with the motor outside the cage which makes it intrinsically safe which means it will not blow up from solvent vapors. It is vented to the outside and the fan has the ability to move enough air based on the calculations I did, given the distance to the vent using corrugated piping. The air from the booth flows through a small furnace filter before it gets to the fan. The filter is common size and costs only $3-4. I also built the small turntable using a bought base and adding some plywood to it $15. There is a that goes across the top of the opening for hanging small parts to dry. There is a light installed, the  hot incandescent bulb helps the drying process. I have a curtain that I can hang on the front so dust doesn't get in while the paint dries. I use toilet paper cardboards to hold boxcars and engine shells for painting.

The nuts and little wood block are used to set a car on. The bolsters or trucks rest on these. The 2 little tubes on the left is large pieces of heat shrink tubing that I use to cover couplers

You can see the hook in the roof which I use to hang things to dry. If you look close you can see the wire across the front to hang parts on. The furnace filter at the back slides in from the top. The tooth brush is what I use to help clean my brush.

Shows the switch for the fan and the ducting coming off the fan

Shows the rest of the ducting

The hanger on the side for my brush

Shows the paper rolls as model holders. They are very stable.

Air supply comes from my little compressor that is in the garage that was piped into the basement when the house was built. There is a regulator and filter on the line in the basement. There is a quick connect to the basement line so I can easily use it for other things. The pressure on the compressor is set to about 50 psi and the one in the basement is set to around 40 psi. By having the 2 regulators the pressure doesn't fluctuate much. It also protects incase I have the compressor set for 110 psi and connect it to the basement. I can also control the amount of air I want right on my brush  because it is double acting.

Materials you are painting takes some consideration. I have painted plastics, cardstock, brass, styrene, abs, derilin, wood, resin, metal and beer cans. All with acrylics. I have never had many problems. The only one that can really give you problems is resin or any plastic that has mold release on it. This is an easy fix by just wash the parts with with soap and water and rubbing it with a toothbrush, then rinsing and putting it aside to dry so dust can't get on it. This step should be done with anything you are going to paint to get rid of dirt and finger oils. Then you are good to paint. You can paint brass with acrylics and doesn't need to be cooked in an oven. Let's think about the old school approach to brass. I have been told how you have to do all these steps and this and that to make the painted surface tough, mmmmm so it can sit on a shelf and never be touched??? Of all the models 150+ that I have painted and decaled including brass that run and are handled on my layout I have never had paint come off of anything ever nor have I ever even have a decal problem from handling. The only thing I ask is you use my wipes to clean your hands so I do not get greasy fingerprints on models.

Take the time to practise. This can be very enjoyable. You open 2 beer cans drink the first one wash it dry it with a cloth. Now start to paint the can trying different things as you go like distance from the can, air pressure, paint flow. You are still drinking the 2nd beer right... you will need that can to. Once the paint has dried you should try masking as square off and then paint the inside a different colour. The lesson here is about masking and not going under the edge with paint. Then remove the masking without pulling paint off the can. The paint doesn't stick well with acrylics so if  you can get the masking off this then you can get it off anything else. Have you finished  the 2nd beer...good now you can practice on this can. You may not want to open a 3rd beer right away. Pop can be substituted for beer. It should be an aluminum can though. 

There are some safety tips you should be aware of. Breathing atomized paint is not good for you. The vapours given off by solvent based paint is not good for you and can cause explosions if used in the vicinity of electrical spark from contacts or open flame appliances such as water heaters and furnaces. Over the years I now have an allergy to AC glue if I use very much of it. So if I have to do a lot  I will do that glueing using my paint booth to remove the vapours. Care also has to be taken if you are using lacquer thinner to clean up your brush.

I also have a post on How I make my paint and brushes last which is worth a read if you have not already.

No comments:

Post a Comment