Why 3D Prints Leak: Draining, Repairing, and Saving a Hollow Resin Cow
The process of troubleshooting and saving an improperly post-processed print from another service.
Jennifer L Tallman
9/12/20263 min read
This past spring, I was asked to fix a hollow resin print that came from another printing service. The model had been sitting on a shelf for months, seemingly fine. But when the owner’s artist finally started prep work, a plug popped out of the belly and uncured liquid resin began leaking out. They reached back out to the original printer for help, but the printer offered no quality guarantee and refused to assist.
A mutual friend in the hobby who bought my prints before—messaged to ask if this was something I could fix. I couldn’t promise I’d be able to save it, but I wanted to try. Disasters like this are the exact reason so many traditional artists refuse to work with 3D prints, and honestly, I don't blame them. Uncured resin trapped inside a shell will eventually off-gas, build pressure, expand, and crack the print from the inside out. Worse, raw resin is a skin sensitizer and toxic to handle without proper safety gear.
I want to use this project to help educate collectors, artists, and maybe even newer printers coming up in the hobby on why uncured resin happens and how to avoid it.
When the print arrived at my studio, the active leak at the belly plug had stopped, but I could see shiny, wet patches near the ears and belly where resin had seeped through. There was also a sizable crack going to the plug hole in the belly. I imagine this is where the damage started before the plug had come out with sanding.
Next, I needed to check every potential "blind pocket" in the digital file geometry. I drilled holes into the feet and fished out more trapped supports from inside the legs. The horns were drilled and turned out to be completely solid (which is good), but when I poked a hole in the tail, a pocket of trapped liquid resin came pouring out
My Technical Takeaways on This Print:
Unchecked Auto-Hollowing: Hollowing large resin models saves material and weight, but auto-hollowing software is notorious for creating trapped islands. On this piece, the body hollowed, but a narrow section of the tail closed off before widening out again at the tip. That created an isolated "bottle" of raw resin inside the tail tip with nowhere to drain. Printers need to manually slice through every layer to check for hidden voids. This often happens in legs and other thin areas.
Over-Supporting Interiors: Supporting hollow structures prevents print failures on the bed, but if internal supports are too dense, the wash-and-cure process becomes impossible. If raw liquid resin can’t be washed away and exposed to UV light, it will sit inside the print indefinitely—waiting to ruin an artist's paint job months down the road.
Check out the video below for a visual walkthrough of the rescue process! It was a time-consuming fix, but I’m glad I was able to get this piece fully drained, cured, patched up, and safe for the artist to work on with confidence.
My first step was surgery: I cut open a large hole around the belly plug hole and crack, and another in the neck. I chose a flatter section of the neck where patching and blending the sculpt later would be easier. Once I opened it up, the root problem was clear—the interior was completely crammed full of print supports. Internal supports are normal, but when they’re packed this densely, wash alcohol can't circulate to clean out the raw resin, and UV light can't penetrate to cure the interior walls.
I spent several hours pulling supports out of the cow with needle-nosed pliers and ended up with an impressive pile. Every single piece was soft, sticky, and completely uncured.
Once I was confident every cavity was exposed, I thoroughly flushed the interior with 99% isopropyl alcohol, let it fully dry, and then cured the inside using a combination of a narrow UV flashlight and a high-power UV lamp.
With the internal structure clean, dry, and rock-hard, I tacked the cut-out resin pieces back into place with two-part epoxy. Then I packed the seams with Apoxie Sculpt, blended the texture, and sanded everything smooth using my rotary handpiece.
