Masking fluid - graphigum
Graphigum is a water-soluble protective coating which is used to cover parts of a model that should not be painted. When it dries, it forms an elastic layer that can be removed after painting the model. Usually it is produced in a milky liquid consistency, which is applied to the model surface.
A few years ago I bought a masking fluid in a hobby shop. It is manufactured by Lefranc-Bourgeois focused on art tools. The price of one bottle is around 3€ - 4€. In this case, the price is very acceptable because volume of fluid is 75 ml. I use it already for five years and I have used only a half so far. Primarily, this product is intended for acrylic and watercolor paints, but I tried even synthetics paints without problems.
There is also a lot of other products from different manufacturers. For example Agama, Humbrol or Vallejo. Some hobbyists also like Art Masking Fluid manufactured by Winsor & Newton Arts, that ranks among the top producers of watercolor paints. Most products have similar characteristics, so it's up to you which you choose.
What we are going to need
- a cap from mineral water, soft drinks, beer, or just any other small bowl,
- a brush (preferably an older one or a low quality brush).
Before opening the bottle I recommend to shake it to mix sediments properly. Pour a small amount of fluid into the container. The fluid quickly evaporates and dries. If we poured out a larger quantity then we would not be able to use it all within 5-10 minutes and the liquid would dry. Never leave the bottle open for a long time!
When we apply graphigum to a clean unpainted plastic part, we should first degrease it. If we didn't do it, then fluid would not adequately cover up all required places. When we apply the fluid to already painted surface, we should be really sure that the paint is sufficiently dried. Otherwise we could have difficulties with removing the dried graphigum layer.
We pick up the graphigum with a brush and transfer it to the model surface. It can be spread very simply. If we want to be sure that we covered everything properly, then we can apply another layer. We have to clean the brush under running water with soap right after when we are finished. I once forgot to wash my brush and it was quite difficult to remove the dried graphigum.
Wait at least 30 minutes after you spray the model with paints, then you can very easily remove the graphigum layer. According to the manufacturer's instructions it is best to do it with a rubber, but in my experience cotton sticks and wooden skewers proved useful too.