Mastering Model Building: Sandpaper and Files

Amongst the basic model building skills, sanding and filing are topics that no modeler can bypass. In this article, we'll explore the different types of sandpapers and files available, their pros and cons, and some handy tips for using them effectively. So grab a cup of tea (maybe some sandpaper and files too), sit back, and let's take a journey into the world of sanding and filing.

Let’s start with a question:

What is the Difference Between Using a File and Using Sandpaper?

This is a question I use a lot to help beginners to choose between the two— if you know the difference, feel free to use either; but if you don’t, maybe it's better to start with sandpapers.

(Most) Files Only Cut in the Forward Stroke

The fact that files only cut in the forward stroke can be a disadvantage for beginner modelers because it requires a lot more learning and practice to execute a satisfying surface finish and execute safely.

Here are some of the specific challenges that beginner modelers may face when using files:

1. Lack of Precision: Beginner modelers may find it difficult to handle files with a consistent and precise motion, especially when working on wide areas (wider than the width of the file), as well as thin long areas (where either a broader file or a narrower file are both risky). This can result in an uneven surface or unintentional damage to the plastic model.

2. If things go wrong, they’ll go really wrong: When a surface is damaged by files, there are more likely to be deep gouges and massive score marks or an entire chunk of plastic missing.

3. Steep learning curve: The difficulty itself becomes a difficulty. As a beginner, when you need to remember “this thing only cuts this way”, “steeeaaadddy…” and trying to think “where I need to go and which part I need to remove” is mentally more stressful in conjunction with other challenges you are facing.

Don’t get me wrong, I personally use files way more often than my sandpapers when I build, all I’m saying here is, that they are harder to use well and easier to mess up. But if you are experienced, both sandpapers and files are powerful tools!

Sandpapers are generally considered to be a more friendly choice for beginners. Here are some pros and cons of using sandpapers over files:

Pros of Sandpapers:

1. Ease of Use: Sandpapers are easier to use than files because they don't require as much learning and experience. Unlike most files, they cut and remove material in all directions, and in all strokes— you might not get a top result, but also less likely to have nasty file marks over your model.
2. Versatility: Sandpapers come in various grits, ranging from coarse to fine, which allows for a wide range of applications. They can be used for heavy material removal, smoothing out rough surfaces, and cutting paint before polishing. Sandpaper can also be cut or folded into different sizes and shapes, as well as using them attached to a sanding block.
3. Reduced Risk of Damage: Sandpapers tend to be damaged before the part when you apply too much force, this means it is less likely to cause lethal damage to the plastic model compared to files, which can easily gouge or scratch the surface if not used properly.

Cons of Sandpapers:

1. Sandpaper is more of a consumable compared to files: Sandpapers do wear out faster than most files and require constant resupply.
2. More Time Consuming: Sandpapers can be more time-consuming to use than files because they may require more sanding to achieve the desired result.

Grits

In sandpaper, grits refer to the size of the abrasive particles that are attached to the paper. The term grit is used to describe the coarseness or fineness of the sandpaper. The grit number indicates the number of abrasive particles per square inch of the sandpaper.
The most common grits used in sandpaper range from around 120 to 1000, with the lower numbers being coarser and more abrasive, and the higher numbers being finer and less abrasive.

Here are some of the common ones we have on the bench:

1. 600 Grit: This grit is considered to be a coarse sandpaper and is often used for quick material removal. It can be used to quickly remove mold lines or rough areas of the plastic parts, allowing the modeler to shape the plastic to the desired form. This grit should be used with caution, as it can remove material quickly but also leave visible scratches on the surface.
2. 800 Grit: This grit is considered to be a general-purpose sandpaper and is often used for the general smoothing and shaping of plastic parts. It provides a good balance between material removal and surface smoothing, making it a suitable choice for many stages of the construction process.
3. 1000 Grit: This grit is considered to be a fine-grit sandpaper and is often used for surface preparation. It can be used to remove the scratches left by the coarser grits and to further refine the surface of the plastic parts. This grit can be used before priming and painting to ensure a smooth, even surface that will accept the paint well.

Tips on Choosing the Right Grit Sandpaper

Pick the coarsest one possible

Many people think it is always safer to use finer sandpaper, but the truth is probably a bit of a surprise. A coarser grit sandpaper (such as 600 grit) can remove material faster, requiring less pressure and fewer passes, but let’s say if you use 1000 grit for the same situation, you will require to do a lot more passes, pressing down harder as you rage and wonder why it's still not flat, by the time you realised something is not right, you will see the originally crisp and clean part is now blobby with all the edges rounded off. Therefore, assess the situation, and start with the coarsest grit you can afford.

Try not to skip the grits

Follow the order of coarse to fine (400, 600, 800, 1000) as each grit progressively covers and refines the surface created by the previous grit. You may be able to get away with it during the basic building phase, but if you are prepping for polishing a shiny sports car, this is a corner I would not recommend cutting.

Wet Sanding

Wet sanding is a technique commonly used just as they were used in industries, especially when sanding paint layer.

1. Reduced heat buildup: Sanding generates heat, which can cause the plastic or paint to become soft and “sticky”. By sanding the plastic while the sandpaper is wet, the heat generated is reduced, which helps to prevent clogging or unpleasant friction caused by softened plastic/paint.
2. Longer sandpaper life: Sanding dry can cause the sandpaper to clog quickly with debris, which reduces its effectiveness and shortens its lifespan. When sanding wet, the water helps to wash away the debris, which can help the sandpaper last longer.
3. Smoother surface: Sanding with wet sandpaper can result in a smoother surface, as the water helps to lubricate the sandpaper, making it easier to achieve a smooth, even finish.
4. Less dusty: Obviously when sanding wet, the dust created from the sanding is collected by the water and not flying everywhere, your lungs and the people living with you (of course, their lungs too) would really appreciate this as well.

Sanding Sponge

Sanding sponges are a type of sanding tool that consists of an abrasive material attached to a foam sponge, such as the range supplied by Tamiya, or sometimes the abrasives are attached to a fabric backing, then attached to a sponge, such as the range from Godhand. The foam sponge provides a cushioned, comfortable grip for the user, and allows for easy sanding of contoured or irregular surfaces.

Mastering Sandpaper and Files for Model Building

Sanding and filing are techniques every modeler will need to master, and the points covered here are just a little overview for you to get started. Fortunately, these are also skills you will have lots of opportunities to practice and perfect.

Whether you opt for the precision of files or the versatility of sandpaper, remember to choose the right grit, follow a systematic progression, and consider wet sanding for smoother results. Additionally, sanding sponges offer comfort and ease when working on irregular surfaces.

With these techniques at your disposal, you're well on your way to achieving professional-level finishes on your model projects. So, equip yourself with the right tools, practice diligently, and watch your modeling skills soar to new heights.