A maker shared a simple method for adding mass to 3D prints without pausing to insert hardware: design a cavity into the open bottom, fill it with plaster of Paris, and let it set. The plaster adds heft and—because it’s easy to sand and finish—can leave the un
Sometimes you want a 3D print to feel solid—more like a finished part than a lightweight model. But adding that mass usually comes with hassle: pausing a print to insert hardware, sealing openings, or dealing with messy fillers that never quite look right.
Joe Fedewa’s workaround is far more direct. Instead of stopping the print to place weights inside, he builds the base as hollow—specifically by modeling a cavity into the open bottom of the object.
That cavity is then made for one purpose: plaster of Paris. After the print is complete, he mixes the dry plaster with water until it becomes a thick but pourable mixture. The next step is straightforward and slightly nerve-wracking—you turn the object upside-down and fill the cavity. In about an hour, it sets enough to be handled and worked.
There’s heft in plaster of Paris, but the bigger win is what happens after it cures. Fedewa points out that the material is friendly to post-processing. Any rough spots can be sanded down. and the whole bottom smoothed—so there’s no need to cap it off. If a more durable finish is desired, completely cured plaster can also be sealed with a clear coat.
The idea isn’t entirely new in spirit. The same general concept has been used for reinforcing prints with concrete, producing parts solid enough to make tools. What’s different here is the target: plaster of Paris isn’t just adding weight. It’s also being used to create a presentable surface that doesn’t require covering up.
Other approaches to adding mass to a 3D print exist. including inserting metal balls or chunky nuts. bolts. or other hardware. But they come with extra steps—pausing the print to insert components. sealing off or capping the print. and wrestling with goopy epoxies or resins. Fedewa’s plaster method avoids those complications while staying inexpensive.
In the end. it’s a small tweak to how a print is designed—hollowing the base—followed by a fill. a wait of about an hour. and then sanding where needed. For anyone who’s wanted their 3D-printed parts to feel convincingly solid without turning finishing into a second project. that tradeoff is hard to ignore.
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