Why Finishing Matters More Than You Think

Most 3D printing guides end at the print. But anyone serious about quality knows the real work starts when the part comes off the build plate. A print with visible layer lines, unglued seams, or a dull, porous surface isn't going to impress a client, win a cosplay competition, or hold up as a functional prototype.

Post-processing—bonding and finishing—bridges the gap between a raw print and a professional object. And unlike the printer itself, the right bottle of glue or a can of clear coat costs almost nothing. The difference in results, however, is dramatic.

At Dreaming3D, we run both FDM and resin machines daily. We've tested dozens of adhesives and finish coatings on PLA, PETG, ABS, ASA, and photopolymer resins. This guide is everything we've learned distilled into a single reference.

Types of Adhesives: A Plain-English Breakdown

Before picking a product off the shelf, you need to understand how each adhesive type bonds your plastic. There are three primary categories worth knowing:

Cyanoacrylate (CA / Super Glue)

CA glue bonds by reacting with trace moisture on the surface of the material. It creates a strong, rigid chemical bond in seconds. It comes in three viscosities—thin, medium, and thick—and the choice of viscosity determines the application. Thin CA wicks into tight joints via capillary action. Medium CA is the workhorse for most assembly. Thick CA sits in gaps and won't run off vertical surfaces.

Two-Part Epoxy

Mix equal amounts of resin and hardener and you get a chemical reaction that cures into an extremely hard, impact-resistant bond. Epoxy is slower (5-minute, 30-minute, and 24-hour formulas exist), but it fills larger gaps and typically produces the strongest final bond of any adhesive type. It's the go-to for load-bearing structural joints.

Solvent Cement

Solvent-based adhesives like Weld-On 16 work differently—they chemically dissolve the surface of the plastic, allowing the two faces to fuse into a single piece when pressed together and cured. The result is a true weld, not a surface bond. This makes solvent cement excellent for PLA structural parts that need maximum strength, but it requires careful handling due to fumes.

Material-Specific Glues (3D-Gloop!)

Products like 3D-Gloop! are formulated specifically for FDM plastics like PLA, PETG, and ABS. They act like a targeted solvent cement, creating a welded-style bond that's typically stronger than traditional super glue on matching materials. They carry a shorter shelf life and higher price point, but deliver results that justify the cost for specific applications.

Best Glue for FDM Printed Parts

FDM prints made from PLA, PETG, ABS, and PETG each have different surface chemistries. Here are the top performers by use case:

Best Glue for Resin Printed Parts

Resin prints have a fundamentally different surface than FDM. They're non-porous, ultra-smooth, and highly rigid. This means solvent cements that work by dissolving thermoplastics have no effect. Your go-to is always CA glue—and thin CA specifically excels here because the tight, smooth fit between cured resin parts allows capillary action to draw the glue deep into the seam for a nearly invisible bond.

Critical Rule: Always Fully Cure First

Residual liquid resin on the surface will actively prevent adhesives from bonding. Before gluing any resin part, wash thoroughly in IPA, dry completely, and run a full UV cure cycle. A tacky surface is a bond-killer—no adhesive will stick reliably to partially cured photopolymer.

Quick-Reference: Adhesive by Material

Not sure which adhesive to reach for? Use this matrix as your instant reference:

Surface Prep: The Step That Makes or Breaks Your Bond

No adhesive performs well on a dirty, oily, or overly smooth surface. Before you open any glue, spend five minutes on prep—it's the most high-leverage step in the entire process.

1. Remove supports cleanly. Use flush cutters rather than tearing. Torn support interfaces leave stress micro-fractures in the surface that weaken bonds and create uneven mating faces.
2. Dry-fit first. Always mate the pieces without glue to check alignment and spot gaps. Gaps over 0.5 mm require a thicker adhesive (medium CA, gel, or epoxy). Gaps under 0.2 mm are ideal for thin CA.
3. Sand the bonding faces. Use 150–220 grit to scuff the surfaces and remove any print sheen. You're creating microscopic texture for the adhesive to lock into—not trying to remove layer lines entirely.
4. Degrease with IPA. Wipe both faces with 90%+ isopropyl alcohol on a lint-free cloth. Skin oils from handling are invisible but will prevent adhesion. Let fully dry before applying adhesive.
5. Apply sparingly. More glue is almost always worse. A thin, even layer creates a stronger bond than a thick blob. For CA, apply to one face only and press immediately.
6. Clamp and wait. Clamp with spring clamps, rubber bands, or painter's tape. Initial grip forms in 30–60 seconds, but full cure strength—especially for structural joints—takes 8–24 hours. Don't stress-test early.

Best Gloss Finishes for 3D Printed Parts

Gloss coatings do two things: they protect your print and they transform it visually. A well-applied gloss coat hides layer lines, deepens color, adds a glass-smooth tactile quality, and seals the porous surface of FDM prints against moisture, UV, and handling wear. Here are the top options ranked by performance:

Gloss Strategy: FDM vs. Resin—Different Workflows

For FDM Prints

FDM prints are porous and layer-lined. Your gloss workflow needs to address both issues before applying a topcoat, or the finish will simply highlight imperfections rather than hide them.

For Resin Prints

Resin prints already start smooth—they don't have visible layer lines like FDM. The gloss workflow is shorter but has one critical rule: do not post-cure before spraying if you're using acrylic or urethane clear coats, as UV post-curing after IPA washing can cause surface yellowing that the clear coat will lock in permanently.

1. Wash in IPA, air dry completely.
2. Apply 2–3 light coats of gloss clear coat (UV clear or 2K urethane) in a dust-free environment.
3. Allow full cure time—most coatings reach handling strength in 6–12 hours, full cure in 24–72 hours.
4. For a mirror finish: wet-sand at 3000 grit after curing, then polish with a cutting compound.

Application Tips & Common Mistakes to Avoid

With Adhesives

• Don't use too much CA glue. A thin film is stronger than a thick bead. Excess glue creates a brittle mass rather than a molecular-level bond.
• Accelerator speeds cure but weakens bond. CA accelerator (kicker) eliminates wait time but can produce a more brittle joint and cause white frosting on clear or dark parts. Use sparingly.
• CA fogs resin on clear parts. The vapors from CA curing can create a white haze around joints on clear or transparent resin prints. Work in a ventilated space and apply precise, minimal amounts.
• Epoxy on ABS: scuff aggressively. ABS has a low surface energy. 150-grit sandpaper before epoxy is mandatory, not optional.
• Clamp everything. Even a short-cure CA joint benefits from clamping—movement in the first 60 seconds results in a weak, crystallized bond.

With Gloss Coatings

• Multiple thin coats always beat one heavy coat. Heavy applications of clear coat drip, run, and create orange-peel texture. Apply at 8–10 inches, keep the can moving.
• Wait between coats. Don't rush the recoat window. Applying a second coat over a still-wet first coat traps solvents and causes cloudiness.
• Temperature and humidity matter. Cold air or high humidity slows drying and can cause the coating to blush (turn milky). Ideal conditions are 65–80°F with humidity below 60%.
• Always ventilate. Clear coats—especially 2K urethane—contain isocyanates and other aggressive compounds. Use a respirator rated for organic vapors, not just a dust mask.
• Don't coat a greasy surface. Fish-eye craters in your clear coat mean contamination. IPA wipe before every coating application, no exceptions.

Frequently Asked Questions