Prepping for paint

The secret to any good painted finish is preparation. This process starts with cleaning up any physical issues with your model, such as mould marks (moulding lines, sink-holes, ejector pin marks, etc) either by filing or scraping in the case of seam lines or by filling with putty and sanding in the case of sink-holes and ejector pin marks.

The moulding process

Injection moulding is a fabulous thing. Without it, we would not have the high-quality models that we do. However, the process does have its drawbacks and these require attention when you get ready to finish your model. An example of a multipart mould is shown in the image below:

Image courtesy of the Xaimen JingWei Industry and Trading Co, Ltd
Image courtesy of the Xaimen JingWei Industry and Trading Co, Ltd

No matter how good the mould maker is, there are always going to be seam lines, where the mould joins together, and ejector pin marks as the still-warm part is ejected from the mould. As the mould wears over time (and they do) the seam lines become worse until the mould needs to be replaced. That’s why older injection moulds are not as crisp as newer tooling. Think of the older Revell, Airfix and other 60s kits by comparison to the new kits just coming to the market.

Fixing moulding problems

For seam lines, the simplest solution is to use a hobby knife, or snap-off blade knife to scrape down the moulding lines. Often, this is enough to get a nice clean finish. Some models, however, with a larger number of mould parts (say three and four-part moulds) often require more work on complex and compound curves. There are often undercuts and such where the mould parts cause larger seams. These may need to be worked on by the use of files, and a knife to clean up. This is often the case also on resin mouldings. Where these types of lines are unavoidable due to the nature of the mould (usually silicon).

Jeweller’s files and a hobby or snap-off blade style knife should be among your basic toolset to assist you in cleaning up your model. They also assist in customising parts and in sculpting and refining scratchbuilt and modified parts. But that area of work is for another day.

Fixing scratches, cuts and other marks

Putty is your friend. It must be used judiciously. Too much putty and you run the risk of shrinkage and damage after painting. Too little and you’ll find surface imperfections show during the priming stage. Which is all to the good since we want to remove them before final paint goes on to the model.

I prefer modelling putty, others use car fillers. I have no experience with these fillers and putties but intend to try them as I have begun working on metal projects and they call for these types of putty to properly finish them. So as I gain some experience I’ll pass that along.

Mostly I use my old standby: Squadron Green putty. I mix this with liquid cement to form a thick slurry which I can place onto the model and which with the glue then bonds to the surface. I use dental picks and other small spatulas to move the putty about and into the areas I want. Using a ‘runnier’ mix also means there is less putty to remove in the final step before priming.

Sanding and final surface prep

Wet sanding is my preferred method to finish the surface of a model. I find I get a better finish this way.

This is a work in progress. So bear with me while I add to the pages over time. This site is after all a labour of love; not a love of labour.

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