Hi, when reading articles on how others have made their models a term keeps popping up. Sealing the model . As I understand it it's usually done before painting but after construction. But what is it, why do you do it and how do you do it ??

There are 2-3 "sealings" that may take place. (In this order)
The first is a gloss coat to give a smooth finish before decals are applied and before any weathering has been done.
Some people apply one or more gloss coats over the decalled model before any weathering takes place. This will make the decals look more painted on by hiding the carrier film.
After weathering, a final coat of flat is aplied to give a uniform non-gl;ossy finish to the model. Of course, if the prototype had a glossy finish, a gloss or semi gloss finish would be appropriate at this point.

If you are referring to the process prior to painting but after construction, that would be priming. Priming serves several purposes:
1) it gives the model a uniform base coat for painting over.
2) it will show any imperfections in the surface i.e. pitholes and blemishes.
3) if you work in multimedia i.e PE it prepares the metal surfaces to accept a paint coat.
You can use any brand of paint and also any color to prime your model. I personally use flat black laquer primer that I apply with an airbrush. I use the flat black simply because in addition to the above mentioned uses of a primer, the black provides an undershadow for the subsequent colors I apply. I hope this helps.

Mike

If I may add, when sealing a model, be aware of what kind of model you're working on.

Cars: gloss
Aircraft: semi-gloss or flat
Ships and armor: flat

If you are referring to sealing as protecting the final finish, then a clear coat, be it flat, semi-gloss or gloss is what you use. I use Testors Clear Flat to seal my kits and figures. It does not react with paints, etc. and completely disappears. You could also use Artist Clear Flat, which most art stores will sell. I would test it before applying it to a model, but I think it is the same stuff as the Testors Clear Flat.

As for sealing, if you are sealing a resin or white metal figure or kit prior to painting, etc. then use whatever you have handy, but it should be an enamel or lacquer paint that will bite into the surface and privide a base for your paint to stick to. I also prime all of my vehicles with a light coat to find blemishes, etc. and privide a pre-shading, as mentioned above.