The short version
"Wet" and "dry" carbon describe how the carbon fabric gets its resin — the plastic that hardens around the fibers. Wet layup means liquid resin is applied to the fabric by hand (or machine) during layup. "Dry" carbon — properly called prepreg — uses fabric that arrives pre-impregnated with resin from the material supplier, then gets cured under heat and pressure in an autoclave. Same carbon fibers, different process, different results and costs.
How wet layup works
The fabric is laid into a mold, liquid resin is brushed or infused in, and the part cures at room temperature or in a low-temperature oven, sometimes with vacuum bagging to pull out air. It's the simpler, lower-equipment process: no autoclave, less energy, faster turnaround. The trade-off is consistency — resin distribution depends on the operator's skill, so weight and finish vary more part to part, and the resin content (and therefore weight) tends to be higher.
How prepreg ("dry") carbon works
Prepreg fabric comes with a precise, factory-controlled amount of resin already in it — no hand-mixing, no guessing. Layers are cut, laid into the mold, vacuum-bagged, and cured in an autoclave: a pressurized oven that applies heat (typically around 120–180°C, varying by resin system) and several atmospheres of pressure. The pressure squeezes out voids and excess resin, producing a part with a higher fiber-to-resin ratio — meaning lighter weight for the same strength and a more uniform, high-gloss-capable finish.
What autoclave curing actually does
The autoclave's heat triggers the resin's chemical cure; its pressure consolidates the laminate, forcing out trapped air and excess resin. The result is lower void content and more consistent mechanical properties than room-temperature curing. It's also why prepreg parts cost more: autoclaves are expensive capital equipment, the material has a refrigerated shelf life and must be used before it expires, and the process takes skilled labor plus energy. You're paying for equipment, material handling, and consistency — not just the word "dry."
Visual and weight differences you can actually check
- Weight. For the same part geometry, a prepreg autoclave part is typically lighter than its wet-layup equivalent because it carries less excess resin. Ask the supplier for the actual part weight — it's the hardest spec to fake.
- Weave consistency. Prepreg parts tend to show a tighter, more uniform weave with fewer distortions around curves. Wet layup can show slight weave shifting where the fabric was worked into complex shapes.
- Surface finish. Both can be glossy — gloss comes from the clear coat and polishing, not the layup method. Don't judge the process by shine alone.
- Back side. Flip the part over. A clean, uniform back side suggests controlled processing; heavy resin pooling, dry spots, or rough patches suggest hand layup with less process control.
How to read a listing's material claims
Listings use these terms loosely, so translate carefully. "Dry carbon" should mean prepreg + autoclave cure — ask the seller to confirm both. "Wet carbon" or just "carbon fiber" with no process stated is usually wet layup. "Carbon look" or "carbon style" typically means a vinyl wrap or hydro-dip over another material, not structural carbon at all. "Forged carbon" is a different process (chopped fibers in a molded part) — neither wet nor dry layup. If the listing won't name the process, treat the claim as unverified.
Questions to ask the supplier
- Is this prepreg with autoclave cure, or wet layup? (Ask directly — the answer should be immediate.)
- What is the actual weight of the finished part?
- Can you share photos of the back/unfinished side of the part?
- What resin system and cure temperature do you use? (Varies by supplier — you're checking that they know, not grading the number.)
- Is the weave 2x2 twill, plain weave, or forged? What fiber weight (e.g., 3K)?
- Do you have a video of the part, or of production? A confident supplier shows the work.
Which should you buy?
Neither process is "fake" — they're different tools for different jobs. Wet layup parts cost less and are perfectly fine for cosmetic aero (splitters, spoilers, mirror caps) where ultimate strength-to-weight isn't the point. Prepreg autoclave parts cost more because the process costs more, and they make sense where weight, consistency, and structural performance matter. Match the process to the part's job, verify the claim with the questions above, and pay for what the process actually delivers.