Soluble Supports: PVA and BVOH

What soluble supports are for

Ordinary supports are printed in the same plastic as the part and broken off afterward, which scars the surface and is nearly impossible inside cavities. A soluble support is printed in a second filament that dissolves in water, so the support simply washes away. Prusa calls BVOH and PVA ideal for supports on models with complicated shapes, where regular supports are hard to remove. For the support basics, see Supports and Overhangs.

You need hardware that can print two materials in one job: a multi-material unit, a tool changer or a second extruder. Prusa lists this as a requirement. See Multi-Material Systems and Purge Waste.

Which main material to pair it with

Prusa recommends PLA as the main material, because PLA prints at similar temperatures. Other support filaments publish their own compatibility. Polymaker's PolyDissolve S1, for example, is a water-dissolvable support made for PLA, TPU, PVB and nylon based filaments from its own range, and its data sheet rates how well it supports each Maker spec:

Main material (Polymaker products)	PolyDissolve S1 rating
PLA, PVB, TPU, nylon	Supports the model very well
PETG	Generally supports, depending on geometry
ABS, PC	Does not support the model

That table applies to that maker's products. For any other pairing, check the support filament's own data sheet before committing a long print.

Two makers, two sets of numbers

Setting	Prusa knowledge base	Polymaker PolyDissolve S1 TDS
Nozzle	195 °C for PVA+, 215 °C for BVOH Starting point	215 to 225 °C Maker spec
Bed	60 °C Starting point	25 to 60 °C Maker spec
Cooling fan	Not specified	On Maker spec
Drying	Not given in the article	80 °C for 12 hours Maker spec

Use the figures for the spool you have.

PVA versus BVOH

• Clogging: Prusa says PVA is more prone to clogging the nozzle than BVOH.
• Bed grip: both stick to the bed less well than standard materials; BVOH sticks slightly better.
• Dissolving: Prusa gives roughly 20 grams (milliliters) of water per gram of BVOH Rule of thumb.
• Cost: Prusa lists high price as a drawback of both, with PVA usually the cheaper of the two.

Prusa describes both as non-toxic and odorless when printing, and as more suitable for advanced users.

Moisture: the main cause of failure

Prusa calls both very hygroscopic and says they should be kept as dry as possible, stored in a dry box. Its drying article lists PVA and BVOH among the materials that absorb the most water. Wet soluble filament is prone to clogging and to tangling in the extruder gears, per Prusa. Polymaker highly recommends printing PolyDissolve S1 from its dry box and storing it in the resealable bag. Treat a soluble spool as something that lives sealed, comes out only to print, and goes straight back. See Drying and Storing Filament.

Slicer settings that matter

• Support gap: Prusa sets the Z distance between soluble supports and the model to 0 mm Starting point, which it says gives underside surfaces almost as good as top surfaces. With regular supports you need a gap to break them off; here you do not. See Support Settings.
• Purging: Prusa lists larger purge volumes as a drawback, and warns that frequent filament changes can leave PLA in the support, which can stop it dissolving fully. More purge reduces this.
• Bed contact: Prusa advises against printing BVOH or PVA directly on PEI, where it grips poorly. Choose an orientation that keeps soluble material off the bed, or print a 1 to 2 layer PLA raft first Starting point; BVOH and PVA stick much better to PLA than to PEI.

Dissolving the supports

Prusa says dissolving takes several hours, depending on the ratio of material to water, and that warmer water helps but it cannot be too hot. Keep the water below the temperature at which the main material softens, which for PLA is about 60 °C Rule of thumb according to Prusa's PLA guide; see PLA. For disposing of the used water, follow the support filament's safety data sheet and local rules.

Common failures

What you see	Usual cause	Where to go
Nozzle clogs on the soluble tool	Wet filament; PVA clogs more readily	Dry it; Clogged Nozzle
Filament tangled in the gears	Wet, soft filament	Dry and reload
Supports will not fully dissolve	PLA mixed in from too little purge	Increase purge
Support lifts off the bed	Soluble material printed directly on PEI	PLA raft, or reorient