BVOH vs PVA: choosing a soluble support that matches your filament

Two dissolvable filaments, one job, different behavior

PVA (polyvinyl alcohol) and BVOH (butenediol vinyl alcohol copolymer) exist for one purpose: printing supports, or just the contact layer between support and part, that wash away in water. Prusa's documentation notes that the model itself is printed in a standard material such as PLA. Both require multi-material hardware, such as an MMU or a multi-tool machine, and Prusa frames the whole workflow as better suited to advanced users.

The real split is printability. According to Prusa, PVA is usually cheaper but more prone to nozzle clogging. BVOH is described as stiffer, behaving much better during the print, and sticking a little better than PVA, even though both show inferior adhesion to print surfaces. Prusa's conclusion is that BVOH is the better option, with the trade-off of a higher cost. Your decision therefore comes down to your consumables budget and, more importantly, the main material you print, which the next section covers. If soluble supports are new to you, our page on PVA soluble supports covers the basics before this head-to-head.

Matching the soluble support to your main material

Prusa's first rule is straightforward: the main material and the soluble support must print at similar temperatures. That is why PLA is called the best partner for both soluble filaments. The Prusa material page lists a recommended nozzle temperature of 195 °C for PVA+ and 215 °C for BVOH, with a 60 °C bed, which lands in the same range as a typical PLA. Those figures belong to Prusa's profiles; always check your spool label and the profile in your slicer.

With PETG, Prusa says BVOH is practically the only option in its documented workflow. For PLA, its page names either PVA+ or BVOH. This does not make PVA+ forbidden with every other brand or profile: compare the temperatures and guidance for the exact filaments involved. For ABS, Prusa points to HIPS dissolved in limonene, with safety guidance; it also names PVB soluble in IPA.

Soluble interface or fully soluble support

PrusaSlicer exposes two presets for these materials once the MMU3, MMU2S, or XL multi-tool printer profile is selected, for 0.15 mm and 0.2 mm layer heights. SOLUBLE FULL prints the entire support structure in soluble material. Prusa recommends it for complex geometry that needs a large amount of internal supports, meaning supports that never touch the build plate. SOLUBLE INTERFACE uses the soluble filament only in the dense layers between the support and the model; the rest of the support is printed in whatever main material is loaded.

The soluble-workflow page describes poor adhesion on smooth or textured PEI. The material page identifies smooth PEI and powder-coated satin as the best options while also describing weaker adhesion than on PLA. A best option among sheets can still have limited adhesion; these statements alone do not establish a contradiction. Check the exact profile and sheet. Prusa recommends SOLUBLE INTERFACE when supports touch the plate and also mentions a PLA raft.

Purge volume, default tool, and speed: what soluble changes

Neither the slicer nor the printer can detect where you loaded the soluble filament. Prusa states that PrusaSlicer assigns support or interface material to filament number 5 on MMU2S and MMU3 by default, and to tool 2 on the XL. You can enter any value from 1 to 5; a value of 0 uses whichever tool is already active on that layer. Check this assignment before every job, so the slicer uses the intended filament.

The purge section applies to MMU3 and MMU2S: a 140 mm³ default for combined unloading/loading, with at least 200–240 mm³ suggested for soluble material and sometimes a 240 mm³ minimum when leaving PVA+/BVOH. It advises increasing the value if residue remains. The material page describes residual PLA in supports as one cause of incomplete dissolution. The MMU configuration section for MK3S/+ also cites profile limits of 4 mm³/s for soluble material versus 15 mm³/s for PLA. Do not transfer these MMU figures to XL without checking its profile.

Dissolving and cleaning without damaging the part

Prusa's procedure starts before the water: remove as much support as the geometry allows while the print is still dry. Then submerge the part in warm water, 45 °C maximum, for a few hours up to overnight. The supports should then come off fairly easily, sometimes with tools. Once the part is clear, a second soak of 10 to 20 minutes followed by brushing, a small stiff toothbrush works well according to Prusa, clears the remaining PVA+ or BVOH debris.

Prusa says duration depends on the material-to-water ratio and temperature, giving roughly one gram of BVOH per 20 g of water as a reference. This is not a guaranteed duration for a particular cavity or support mass. If supports contain PLA traces, its page suggests reviewing purge. For your record, note support amount, bath and observed residue; this suggestion helps compare your trials without turning a documented time range into an achieved result. It is a record of observations rather than a new dissolution method validated for every soluble grade.

Keep soluble filament dry

Prusa describes PVA and BVOH as very hygroscopic and moisture as a risk to adhesion, nozzle passage and feeding. It recommends returning the spool to its sealed bag with silica after use. Its guide describes possible deterioration over months if dry conditions are not maintained, without supplying a shelf life for every spool or workshop. Keep the exact product's instructions with your storage plan. An observed feeding fault alone does not measure water content or determine the remaining shelf life of that spool.

Prusa's recommendation is to print from and store these materials in a drybox. Our pages on passive filament dry boxes and on choosing a filament dryer cover the usual setups. On MMU2S and MMU3 for the MK3S, Prusa adds two cautions: a very precise IR sensor calibration, because the soft filament's diameter deforms under excessive idler pressure, and keeping an eye on filament tips that inevitably string while the main material prints. To budget the full kit, soluble spool, drybox, and desiccant, the startup budget tool adds up each line item without guesswork.

Sources and limits

• Prusa Knowledge Base — water-soluble workflow, MMU2S/MMU3 and XL
• Prusa Knowledge Base — BVOH/PVA material and storage guidance

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.