Dry carbon vs wet carbon comes down to how the resin gets into the fabric. Dry carbon is prepreg, fabric that arrives already impregnated with a measured amount of resin and is cured in an autoclave under heat and pressure. Wet carbon, done properly, is VARTM, dry fabric laid into a mould with liquid resin pulled through it under vacuum. Dry carbon is lighter, stiffer and more consistent. Wet carbon is cheaper to produce. And the biggest real-world difference between two parts is often not the process at all, it is what sits underneath the visible weave.
I'm Riley Baginski, founder of RB Innovations. I first published this guide in April and I've rewritten it from the ground up, because the original described wet carbon the way a lot of the internet still does, as cloth brushed with resin by hand. No reputable carbon part on the market is made that way, and it gave you the wrong picture. This is the version I stand behind.
What is dry carbon (prepreg)?
Prepreg starts as carbon fabric with the resin already in the weave, in a precise ratio set by the company that produces the fabric. Because the resin is already there, the fabric has to be kept in cold or frozen storage until it is used, otherwise it starts to cure on the roll.
The fabric is cut to shape, laid into the mould, and vacuum bagged to hold every ply hard against the mould surface. Then it goes into an autoclave and is cured under high heat, typically 120 to 180 degrees Celsius, and high pressure, typically 6 bar or more.
That combination is what makes dry carbon what it is. You end up with roughly 60 to 70 percent fibre by volume, very few voids, and the best strength to weight you can get from carbon. The catch is the equipment. When I priced up what it would take to produce parts myself, the autoclave alone ran to six figures, before freezer storage for the fabric. Even a modest oven cure setup with no autoclave came to around $14,000 before a single part existed.
What is wet carbon? VARTM explained
Wet carbon starts with dry fabric, no resin in it yet. The fabric is cut and stacked into the mould in plies. The first ply against the mould surface is the cosmetic layer, the weave you see when the part comes out. The plies behind it are structural.
A vacuum bag is sealed over the stack, the air is drawn out, and liquid resin is pulled through the fabric under vacuum, infusing the whole layup evenly in one shot. That is VARTM, vacuum assisted resin transfer moulding, also called vacuum infusion. It cures at room temperature or with mild heat, so no autoclave is needed.
The result is a good fibre ratio, roughly 45 to 55 percent fibre overall, low to moderate voids, strong mechanical properties and a good surface finish. It costs far less to set up than prepreg, with no autoclave, no cold storage and cheaper fabric, which is why wet carbon parts sit at a lower price.
Is wet carbon hand laid?
No. The term "wet layup" gets thrown around as if it means someone rolling resin onto cloth with a brush. That describes open mould hand layup, which is not how quality wet carbon parts are made. VARTM is a controlled, repeatable process, and there is nothing sloppy or amateur about a well made infused part.
Same process, different stack: full carbon vs carbon over fibreglass
This is the part most dry vs wet articles skip, and it matters more than the process name on the listing.
Almost every budget and mid-tier wet carbon part sold today is a carbon surface over fibreglass structural plies. The first ply against the mould is carbon, so you get the weave. The plies behind it are fibreglass, a cheaper structural core. The whole stack is then bagged and infused exactly the same way. It looks like carbon, but most of the panel by volume is fibreglass.
The higher spec version is full carbon VARTM. Every ply in the stack is carbon fibre, surface, structure and backing. Same vacuum bag, same resin infusion, same cure, just carbon all the way through.
So carbon over fibreglass is not a different manufacturing process. It is the same VARTM process with a cheaper fabric stack. That is not automatically a bad part, fibreglass backing is a cost decision and plenty of those parts look good and fit well. The problem is paying full carbon money for one without being told. If I ever release a wet carbon part, every ply in it will be carbon.
How to tell if a carbon part is carbon over fibreglass
Flip it over. The most common single tell on the market is a back face painted a flat, solid, opaque black. Sellers do it to hide the fibreglass under the cosmetic carbon ply. A full carbon part has no reason to be painted on the back, because the dark grey carbon weave shows naturally through the resin. I go into more detail on what a painted black back face is usually hiding, but it is the first thing I look at on any part.
If the back is not painted, the other tells are:
- A translucent off-white or yellowish layer on the back, where resin has soaked into fibreglass cloth.
- Pale, almost translucent material at a cut edge or through a mounting hole. Carbon plies are dark grey to black right through the cross section.
- A part that feels heavier in the hand than you'd expect, because fibreglass is denser than carbon.
- A duller, deader sound when you tap it compared to a full carbon panel.
Is dry carbon stronger than wet carbon?
Per gram, yes. More fibre and fewer voids means more stiffness and strength for the same weight, and more consistent properties from one part to the next. A full carbon VARTM part is still a strong, light part though, and on a cosmetic panel the gap between a good full carbon infused part and a prepreg one is measured in grams, not kilograms.
The bigger weight jump is between full carbon and carbon over fibreglass, because the fibreglass plies add density without adding the stiffness carbon would. On a street car's interior trim or engine bay cover, the difference you'll actually live with is finish consistency and how the part ages, not lap times.
Why does dry carbon cost more?
Three reasons: the autoclave, the cold storage and the fabric itself. Prepreg fabric costs more than dry cloth and liquid resin, it has a limited shelf life once it leaves the freezer, and autoclave time is expensive to run. Both processes share the other big costs, a dedicated mould for every design and a minimum run, which I break down line by line in why a proper carbon part costs what it does.
Where does forged carbon fit in?
Forged carbon is a purpose-built prepreg forged carbon fabric, short irregular tiles of carbon pre-impregnated with resin and set in a random orientation, laid into a mould and cured under heat and pressure. It is not chopped offcuts or shop scraps. Because it is a prepreg fabric, forged sits on the dry side of this comparison.
Forged and twill are both real carbon with different character. Twill is the classic repeating diagonal weave, forged is the marbled pattern that never repeats. Neither is better, it comes down to the look you want.
Dry or wet: which should you buy?
If you're building for weight and every gram is a decision, dry carbon is the answer. For a street car where you want real carbon and a clean finish, full carbon VARTM is a good buy. Carbon over fibreglass can be fine too, as long as the price reflects what it is and the seller is upfront about it.
Where the part lives matters. In an engine bay, prepreg has an advantage before you even think about strength, because it was cured at 120 to 180 degrees under pressure, well above anything a normal bay sees. I cover that properly in how carbon fibre handles engine bay heat. It is also why the Barra coil cover in my FG range is specified as dry carbon prepreg. It sits on top of a hot engine and it is the biggest flat panel in the bay, so it is the last place I'd want a fibreglass core.
If you drive a Falcon, you can see what's in the range and what's coming on the dry carbon parts for the Ford Falcon FG and FG-X page. For anything else, the full RB Innovations carbon range is sorted by car.
FAQ
Is wet carbon the same as hand layup?
No. Quality wet carbon is made by VARTM, where dry fabric is stacked in a mould, sealed under a vacuum bag, and resin is pulled through the whole layup under vacuum. Hand layup, brushing resin onto cloth in an open mould, is a different and much less controlled process, and it is not how reputable carbon parts are made today.
Is dry carbon stronger than wet carbon?
For the same weight, yes. Prepreg cured in an autoclave reaches roughly 60 to 70 percent fibre by volume against roughly 45 to 55 percent for VARTM, with fewer voids. A full carbon VARTM part is still strong and light, the bigger drop in performance comes from fibreglass structural plies behind a carbon surface.
Is forged carbon dry or wet?
Forged carbon as used on quality parts is a prepreg fabric, short irregular tiles of carbon pre-impregnated with resin in a random orientation, cured under heat and pressure. That puts it on the dry carbon side. It is purpose-built fabric, not offcuts.
Why is the back of some carbon parts painted black?
Almost always to hide fibreglass. A flat, opaque black back face is the most common sign that a part is a carbon surface over fibreglass plies. Full carbon parts have no reason to be painted on the back, you can see the dark grey weave through the resin.
Does dry carbon last longer in the sun?
Not on its own. Sun resistance comes mostly from the clear coat over the carbon, not the laminate underneath. A prepreg part with a poor clear coat will fade and yellow just like any other. Look for a UV stable clear on either type.
If you're weighing up a specific part and can't tell what you're looking at from the listing, send me the photos, including the back, and I'll give you a straight answer.
Written by Riley Baginski, founder of RB Innovations. First published April 2026, rewritten September 2026 to correct how wet carbon is described.
