While working on a project which involved airbrushing some craft paints, I came across a video for a simple paint filter. It doesn't work for acrylic craft paints straight from the bottle as the paint is too thick to flow through the filter. But then, it's also too thick to airbrush. When the paint has been thinned appropriately for airbrushing, the filter works great. The filter can be used for any airbrush paint to prevent any small particles in the paint being transferred to the object being airbrushed. In reviewing several airbrush related videos, the comments was automotive paint is always filtered before application. Why wouldn't we do the same for our models?
The filter is comprised of 2 easily obtained components. - A brass pipe fitting and a stainless steel pipe filter. In reading about pipe filters, there are various qualities. The ones shown in the photo are stainless steel, stiff and work well. They are available on Amazon.
Total cost for this is around $18 canadian. The pipe filters are the most expensive part with 100 filters for approximately $10 canadian.
Photo 1 shows the parts and part numbers used for the build
Photo 2 shows the pipe filter pressed into the pipe fitting. The pipe filter is 3/4" diameter.The key is to obtain a pipe fitting the same internal diameter as the pipe filter outside diameter so no filter trimming is required. In my case the adapter fitting is a 1/2" female NPT pipe connection on one end with a smaller diameter on the other end. The fitting material is brass to prevent rusting. The smaller diameter on the other end provides an internal landing where the bore size changes for the pipe filter to rest on. I know it's not logical, but 1/2" pipe threads are approximately 3/4" in diameter. The filter is simply pressed in and retained by the pipe threads. Filter removal is as easy as pressing out the filter with the end of a paint brush, dowel, etc.
Photo 3 shows the filter mounted on an airbrush jar.
The filter has been used numerous times. A quick rinse in water of the pipe fitting and screen and it's ready for use again.
Have you been able to airbrush with acrylic craft paints? I would be interested in doing that, as they are much less expensive than model paint.
I have used Delta Ceramcoat and Folk Art paints without any problems, they are comparable brands. Maybe not quite as nice to use as Vallejo, for example, but definitely less expensive.
That's really good to know. Would you mind sharing your method of thinning them to the right consistency? I would love to be able to use those in my airbrush!
Thanks, Dave!
I use water from an eye-dropper. There is no set formula, but when I put a certain amount of color in the airbrush paint cup, I always start by adding ten drops of water, then mix it with a brush. Then add a little more if necessary. It might end up 1:1, but that is a guess.
Airbrushing acrylic and water tends to clog the nozzle because it dries quickly, so a lot more cleaning is needed.
I have seen modelers recommend using various products as paint thinners including Windex, Isopropyl Alcohol and even "Future". Have not tried any of them personally.
Here's my approach to airbrushing acrylics. It's a little long winded.
Note: I always pass the thinned paint through the filter in the picture below into another measuring cup. I inevitably filter out some solids which have collected at the top of the bottle. The filtering keeps the airbrush tip from becoming clogged by any paint chunks.
I use the cheap scale in the photo (Amazon special) to measure the weight of paint I wish to use. Normally add about 50% of the volume I anticipate I will require as paint volume into the measuring cup. Using the scale and a plastic pipette to add a thinning agent is much more accurate and controlled than trying to read the markings on a measuring cup.
Then I add about 25% of the volume required using a water / additive thinning mixture. This mixture is 1 part "Golden Airbrush Thinner" + 3 parts distilled water + 4 drops "Liquitex Flow Aid" in a 4 oz bottle. You can also use "Liquitex Airbrush Thinner" instead of the Golden product. The airbrush thinner is very fluid and helps to minimize the acrylic polymer dilution resulting from using 100% water. I suspect you could also increase the percentage of airbrush thinner and reduce the volume of water. The airbrush thinner is not very viscous. The flow aid helps to reduce airbrush tip drying and aids in allowing the paint to level. But you don't want to over add as it will cause the paint to run after it has been sprayed.
Once the initial reducing mixture is added, I perform the "skim milk test" by placing a couple of drops on the side of the measuring cup. If it doesn't run down the inside of the cup in a similar manner as skim milk would run down, I add some additional thinning mixture and repeat the skim milk test. I repeat this process until the skim milk viscosity is reached. This usually takes 3 or 4 iterations.
Once the paint has the skim milk viscosity, it's over to the airbrush parameters. I have two airbrushes with I use. - A badger 350 where I use the largest airbrush tip and a Paasche Model H airbrush were I use the No. 3 tip. Using a sufficiently large tip is key to minimizing tip drying. With the appropriate tip, I set the airbrush pressure to around 15 psi. Note, I use the large braided hoses for both airbrushes rather than the small diameter plastic hoses. The plastic hoses have a large pressure drop, so 15 psi at the regulator is significantly lower at the airbrush. The braided hoses have minimal pressure drop. If the spray pressure is high at the airbrush, air brush tip drying may result.
I've attached a couple of photos where I airbrushed craft paints onto some toy cars for my nieces and nephews. The clear coat was Liquitex High Gloss varnish. For the clear coat, I sparingly add around 10% distilled water and used the largest airbrush tip. It doesn't seem to take much water to reduce the viscosity of the varnish to a skim milk viscosity.
Hope this helps. There are many many recipes on the internet for airbrushing craft paints. Simply adding water will work. But I believe it significantly reduces the bond strength & acrylic properties of the paint. Other chemical such as Windex can also potentially adversely impact the acrylic polymers over time. Future is similar to the the airbrush thinner. It' an acrylic medium. But I have read various articles which indicate straight Future can be tricky to airbrush, so I have stayed away from it. Mixing it with the paint may reduce the difficulties of using it in an airbrush. But I can't comment on this.
-ken
Thank you for the very thorough response. I will have to experiment and see what I can do. I have a single action airbrush from when I was just getting into modeling as a teenager. I've also got a small compressor (non adjustable). The hoses are just the small plastic ones you mentioned.