What are the best sanding and filling tools?

-I know alot of people make their own sanding blocks so I’m wondering what’s the best way to do this. I’m trying to sand a hand-held size foam model, and it’s the first time I’ve worked with foam. It’s difficult to sand concave or convex curves with a flat sanding block sold in stores. I’ve also heard not to use your fingers and to always use some kind of support (so that you only sand the peaks and not the valleys- highs and lows).

  • Another question I have is filling. The same problem arises trying to fill curved surfaces with a flat putty knife or other flat tool, and then trying to sand with a flat block to top it off. Any suggestions for this would be appreciated!

-Find piece of foam
-Go to bandsaw
-Cut one side concave, one side convex
-Apply super 77 to both sides
-Apply super77 to sandpaper
-Let glue dry
-Apply sandpaper to convex and concave sides of foam

this is a very simple way to get a nice curvy sanding block. Experiment with various curves at various scales.

3M also makes brilliant soft sanding pads. these bad boys got me through school. they come in medium, fine, and x fine.


Just get really good at sanding and you’ll never have to fill your models…seriously.

Tools for filling:

Get some painting knives at an art supply store. If you’re not familiar with these, they’re used in acrylic and oil painting. They come in a vast variety of sizes, shapes and flexibilities. If you can’t find exactly what you need, they can be filed, ground or sanded to modify them. I use them for everything from soft to Bondo type fillers.

If you can’t find a local source, you can get them online at places like Dick Blick.

for filling, you could always use a rubber sculpting tool like this, or pull the silicone off the end of a spatula. Just make sure the Bondo, etc doesn’t react with the tool.
sculpting tool.jpg

Thanks for the great responses! I’m going to give some of these a try.

Okay, here are some great tips and photos of tools that I found from caraudiomag.com. (http://www.caraudiomag.com/technical/0510_caep_body_filler/index.html) The tools in this article are used with plastic body fillers (or “bondo”), but can be used for any other sanding or filling application, i.e. urethane/polystyrene foam and joint compound/vinyl spackle filler.

Plastic body filler spreaders are available in different sizes and can also be trimmed to custom shapes and sizes to fit your needs. You can wipe them clean, or leave them soaking in a bucket of acetone.

Rather than just folding a piece of sandpaper and sanding away, glue the sheets of sandpaper back to back with 3M Super 77 spray adhesive (spray both sheets) and cut them into appropriate sizes. Gluing the sandpaper back to back transmits more of your energy into sanding force (no slipping) and gives you a better grip on the sandpaper. For flat areas, gluing the sandpaper to both sides of 3"x 9" MDF blocks makes great disposable sanding blocks. Getting creative and making your own sanding tools (from ABS pipe, metal conduit, etc.) can help make the shaping process much easier.

Hope this can be useful to someone!

Are you trying to make a foam model look like smooth plastic?

Seriously…Isn’t this taught in model shop class? Get dirty and use your hands. Sorry not trying to be a jerk but this is something you can learn by watching the other students in you class and asking you modelshop prof.

Yes, you could say that I want to make a model that looks like smooth plastic. All I want to do is create a model with a high level of finish, like a fiberglass body on a car. I want to do stuff like Luigi Colani or the modelmakers/builders/fabricators of concept cars.

To PackageID: I’m just trying to contribute information to this site. I actually just recently left a school that strictly taught cardboard architecture models as a substitution for a dedicated ID foundations, so I had to look at the sophmores and upper level classmen for advice. Even at the highest level, the models were poor and full of surface imperfections, because the program at the school was so new. I am actually between schools right now, so I’m just trying to find information. I HAVE been getting my hands dirty and I HAVE tried many different techniques and tools just to get a feel for what works best. I’m posting what I have found here because of the lack of info on the subject that I have found on this site.

I like to make things- some people just do! There might be people that don’t have the means or resources to pursue a ‘great’ education in ID, and maybe there’s some people out there that just want to get a head start on things. I believe that’s one of the major benefits of this site and of the internet. People shouldn’t have to sit back and wait for a school/institution to teach them how to do everything; if they want to learn and do for themselves, then so be it!

I’ve had good luck using the Ace Hardware Sanding Sponges
Their a little pricey but I like the results I get. I’ve also glued sand paper to a regular kitchen sponge and that worked fairly well too.

I don’t think that OP ever mentioned being a student. Not every who posts/reads is a student or has access to a model class.

okay…Before I start getting burned at the stake here…First you are right not everyone on this site is an Industrial Designer and I am sorry if I assumed that. I made that comment because this is a fundamental tool that should to be thought in school and I think that many students are not learning how to make finished models like they used to. To me this is a very sad thing.

Back to the question at hand…There are many different techniques for finishing models. A lot of this depends on the media that you are using. I found Bondo Spot Putty to be a great filler on balsa foam. It takes a bit of time but will give you a great surface if you have the patients. As far as the sanding go, sometimes you do have to use you hands in hard to reach spots but for flat surfaces use a block.

I encourage you to play around and you will find what works best for you. There are many books out there on model building as well. Some are on presentation models but also look at the ones on hobby models, they can teach you some really great stuff.

A nice piece of spring steel is always a choice option for large surfaces you want an even finish on, just mind the corners. I’ve lost many - a -hour from a errant steel corner digging into my pretty sanded surface.

Something to consider adding to your “sanding tool kit”; PPE (Personal Protective Equipment).

Inhalation (of vapor or dust) is the primary path of entry into the body. Protect your lungs with a Respirator.

Cheap; dust only (but better than nothing).

Not so cheap; with replaceable organic-vapor (i.e.,paint vapors) and dust filter cartridges. Buy a good one, it will last for years.

Permeation (through the skin) is the second route. Wear gloves; they desensitize your fingers, but are worth getting used to.

Nitrile, not Latex Gloves (buy them by the 100 count at a hardware store).

Protect your eyes. Safety Glasses or a Face Shield, should be self-evident. Especially when grinding fiberglass, wood, metal, bondo, etc. Use in conjunction with an organic-vapor respirator when handling hazardous liquids, i.e., acetone, thinners, paints catalysts, accelerators, reducers, etc.

And one other bit, a tool of a different sort, Information. Learn how to read an MSDS (Material Safety Data Sheet); it describes what is in the material(s) you are using, how to safely handle, store, and dispose of them. Ask for a copy when you purchase materials, the retailer (or wholesaler) is required by law to provide you with a copy if you ask for one. Ask for an MSDS!

MSDS Examples
Download Adobe Reader here;

i.e., Bondo (.pdf format)

i.e., Acetone (.pdf format)

Acetone, paints, thinners, “bondo”, epoxy, fiberglass, graphite, etc. aren’t exactly friendly to the human body. Acetone is particularly nasty, making its way through the skin (defatting and permanently drying it out on the way) and adversley affecting internal organs and the central nervous system.

It is your intention to be occupied doing this kind of work for quite a few years. The effects of these materials are cumulative; you may not feel the them immediately, but you will eventually.

when I first started teaching surfacing workshops in Pro/ENGINEER I called the class Pro/SANDPAPER.

the tools work just like a parametric rasp and filler