Thursday, January 13, 2022

Fill those holes!

If you've ever prepped an artist resin, you've probably encountered pinholes, and you've probably used Bondo to fill them. But is that really the best choice? In today's guest post, NaMoPaiMo's newest staff member, Shauna McDaniel, explores a multitude of pinhole filling options. Thank you so much, Shauna!

Prepping Alternatives to Bondo

by Shauna McDaniel

Bondo has been used in the hobby for ages. It's readily available, does the job it's designed to do, is stable to work over and cost effective. Sounds good, right? Here's the rub: It's noxious. Dust from sanding is dangerous to inhale, so careful ventilation is super important but not necessarily available to the average hobbyist.

One of the popular alternatives is something you'll hear referenced as Messo.  It's a mixture of modeling paste, which is easily found at art stores and basically odourless, and gesso to both thin it for application and help stabilize it so it sands better. I had intended to include it today but it's been so long my paste was concrete. 

This post explores the other easily available alternative products.  All but one have no odour, are soap and water clean up and offer different benefits.  There's also a couple, "so I tried this... don't waste your time tacked on for fun."
I'm going to start with my easy winner. Liquid Green Stuff goes on smooth right out of the jar. It's easy to spread, smooths with water and you can see it in the pinholes. 
It has a slight plastic texture and will flex a bit when you abuse it, but you can both sand and carve it without crumble. It is NOT great in a big gap - use epoxy there - but for straight up open jar slap on use I love it.
Plastic Putty is my easy number two, and if you can get both, do. 
This is my absolute go to for those "Ohh @$#!! I missed something" moments. It dries in seconds and is acrylic based it's super smooth no smell and you do not have to prime it (probably still should but it's stable as all get out). It's super cheap on Amazon, cleans up with water and sands well. It's less fond of the carbide scrapers, but doesn't go all too pieces like some of the others.
Now I use piles of GSW'S products but this one is kinda meh. 
It crumbles really easily, so despite being smooth to handle any adjustments or sanding probably aren't worth it.
The most expensive entry in the straight from the bottle category is also the worst. 
It has a strong smell, isn't water soluble and crumbles if you try to work it after it's dry. I've tried very hard to love it but pfft. Fit for the pit.
Okay, good old two-part epoxy resin - in this case Procreate - was on my desk so I'm including it. This is a micro specific two-part with a more plastic feel than clays like Magic Sculpt. I've smoothed it with a bit of alcohol. You can thin most of them down to a paste with alcohol and they're awesome for the job but extra steps to get organized.
Of course, it's easy to smooth, sands and sculpts well, blah blah blah. It's fantastic.
Soda glue! So this one will work, but because the result is harder than most of our models, sanding it level can be quite frustrating, especially in the beginning. Soda glue also needs to be primed fairly soon after use because something something science or other on that one. It is a decent option, but remember the chemical reaction will burn skin and the off gas is unpleasant so be careful!
Here's an outlier. First of all if you have 3D prints I highly recommend having UV resin and a black light on hand (bondic pen will work!). You can repair broken prints and resculpt missing bits with it, but it's also handy for prepping! 
It is a little fussy to work with, but you can spread it and set it in seconds, then prep as usual. I like to use it on big areas of bubbles or pin holes then set under a light. It sands and doesn't crumble with scrapers. Apply it thinly and build it up in layers.  This will result in less swearing.
Finally, two for the stupid things Shauna tried. This one sounded really great and is a very interesting product. I had hoped that I could spread the powder and spray with water then tada! Yeah... no. It crumbles much too easily under stress and just results in white powder everywhere.
And, of course, heat set liquid polymer. Umm... okay, so the translucent liquid Sculpey is actually nicer to work with than this one. It requires a fine detail heat gun to cook the area, and once done, it doesn't sand well. Also, the rubber texture and primer are not great friends. So another... not exactly what I hoped for.
So now you know all the ways to fill - or not fill - your model's pinholes. NaMoPaiMo is coming. Go forth and prep your models!


  1. This is a great summary! I might try some of these. For what it's worth, I really like Liquitex modelling paste in medium straight out of the jar. Water soluble, sandable, white, dries quickly to a hard finish for very small areas.

  2. Thanks so much for sharing this info! :)