BVOH Butenediol vinyl alcohol copolymer water-soluble support (BVOH)

BVOH (butenediol vinyl alcohol copolymer) is a water-soluble support material, a close relative of PVA. Like PVA, it's never used for a finished part: it's printed underneath overhangs and inside cavities wherever your part material needs something to rest on, then dissolved away in water to leave clean surfaces.

The case for BVOH over PVA is speed and versatility. BCN3D's comparison says BVOH dissolves much more quickly than PVA and leaves less residue, and Prusa's knowledge base notes it sticks a little better than PVA, while PVA is usually cheaper but more prone to nozzle clogging. Verbatim lists BVOH as working best with ABS, PLA and PET, and Fiberlogy names PLA, ABS, ASA and PET-G, a wider range than PVA, which Polymaker rates as unsuitable for ABS and PC.

On our QIDI Max4 and Plus5 printers, BVOH runs through the QIDI Box multi-material unit next to your part material, and QIDI lists it as supported only when dried. Because the printers use a single nozzle, every switch between part material and support requires a purge, adding time and some waste. That's the main reason soluble support costs more on any single-nozzle machine.

BVOH is very hygroscopic, meaning it absorbs moisture from the air, and both Prusa and BCN3D stress keeping it dry. Verbatim also notes it is light- and UV-sensitive. None of this affects your finished part, because the BVOH is gone, but it does make BVOH a premium, carefully handled material in our process.

BVOH's own strength is irrelevant once your part ships, because it's dissolved away. Its job during printing is to bond well enough to your part material to hold overhangs in place, while still dissolving cleanly afterward. Prusa recommends zero Z gap between soluble support and model, so overhangs print onto a solid surface.

Soluble supports affect your part's performance indirectly. They let us orient a part for strength (FDM parts are weaker between layers than along them, so orientation matters) without worrying about whether supports can be pulled out. They also give smoother, more accurate downward-facing surfaces, which can help mating faces and seals.

Long soaks can slightly affect moisture-sensitive part materials such as nylon. BVOH's faster dissolving shortens that exposure compared with PVA, and we dry such parts again before final inspection.

BVOH's temperature behavior doesn't matter in service, because none of it remains on the delivered part. Heat resistance and suitability for a car, outdoors or a dishwasher depend entirely on the material your part is printed in, so check that material's page.

Temperature matters while dissolving. Warm water speeds things up, but Prusa cautions it can't be too hot either, and PLA parts in particular soften if the water gets close to PLA's heat limit. We match water temperature to the part material and accept a longer soak for PLA.

Not applicable to the finished part, since BVOH is dissolved away. Verbatim notes the raw material is light- and UV-sensitive, which is a storage concern for us, not a property of your part.

BVOH is designed to dissolve in plain water and isn't used in contact with chemicals in service. Your finished part's chemical resistance depends entirely on its own material; see that material's page.

BVOH is very hygroscopic. Left in room air it absorbs moisture quickly, and damp filament prints poorly and is rejected by the QIDI Box, which accepts only dried BVOH. Fiberlogy recommends drying at 50 °C for 4 hours, and we keep it in sealed, dry storage between jobs.

BCN3D notes that BVOH tolerates long prints better than PVA, reporting up to 2 days of trouble-free printing in a closed printer, which makes it the safer choice for long, complex jobs. For you as a buyer, the moisture handling shows up only as setup time in the quote.

The finish benefit is on the faces that touched support. With soluble support printed at zero gap, downward-facing surfaces come out smooth and accurate instead of rough and scarred from breakaway removal.

There can be a slight texture difference between supported and unsupported faces, and occasional faint streaks where materials mixed during a filament switch. BCN3D reports BVOH leaves less residue than PVA, which helps with clean, fully cleared surfaces.

We peel away any bulk support that comes off easily, then soak the part in water, changing or circulating it to speed dissolving. Prusa notes dissolving takes several hours depending on the ratio of material to water, with roughly 20 g of water needed per gram of BVOH, so we use generous volumes. Internal channels may need flushing to clear softened material.

On disposal, Verbatim says BVOH waste can go down household drains when diluted with more than 20 times its weight in water, up to 2 kg of BVOH per day, with larger volumes needing professional effluent treatment. Local rules vary, so if you dissolve supports yourself, check with your local sewer authority.

Soluble supports generally improve accuracy on downward-facing surfaces and inside cavities, because overhangs print onto a solid surface rather than drooping. Horizontal holes come out rounder and sealing faces flatter.

They don't change your part material's own tolerances or shrinkage, and holes still tend to print slightly undersized. If the part material is moisture-sensitive, we dry it after soaking before measuring critical dimensions.