How to clean silicone moulds properly is one of those studio habits that separates makers who get consistent results from makers who spend sessions troubleshooting surface defects on new pieces. A mould that has residue from the last pour will transfer that residue to your next cast. A mould stored folded or compressed distorts over time and casts that distortion into every piece you make from it.
I'm Anirudh, founder of Artriso. CALSO ONE is a mineral-acrylic material, which means the residue it leaves in moulds is different from what epoxy or wax makers deal with. This guide covers the cleaning method that works for our material specifically, the situations where standard cleaning is not enough, and the storage habits that extend mould life significantly.
Why mould cleaning matters for CALSO ONE
CALSO ONE leaves a mineral film inside the mould after demould. The film is fine enough that the mould looks clean, but under bright light you can see a slight chalky or powdery deposit, especially in moulds used with pigmented mixes. This film is inert and does not affect the cure of the next pour. But it does two things that matter over time.
First, it builds up. After ten to fifteen pours without proper cleaning, the film is thick enough to affect the sharpness of fine surface detail. Second, pigment residue from coloured pours can stain the silicone, which is cosmetically minor but can transfer a faint tint to the next light-coloured cast if not addressed.
The cleaning method below removes both.
What you need
A basin or sink large enough to submerge the mould. Hot water: 60 to 70 degrees Celsius is the target temperature, which is the range of hot tap water in most Indian homes on a gas heater. Mild dish soap: any standard washing-up liquid works. A soft sponge or microfibre cloth. No brushes with bristles, no abrasive pads, no steel wool, and no sharp implements of any kind.
The cleaning process
Step 1: Demould and remove loose material first. Before water touches the mould, turn it inside out (for flexible moulds) and wipe the interior with a dry paper towel or microfibre cloth. This removes the bulk of the mineral film and any unmixed powder residue while dry, which is easier than doing it wet. For cavity moulds where you cannot turn them inside out, use a soft dry cloth to wipe each cavity.
Step 2: Soak in hot soapy water. Fill your basin with hot water and a few drops of dish soap. Submerge the mould and let it soak for 20 to 30 minutes. The hot water softens any residue the dry wipe missed. The soap breaks down the mineral film. Do not skip the soak and go straight to scrubbing: soaking is what makes scrubbing effortless.
Step 3: Gentle scrub. After soaking, use a soft sponge to work the interior of each cavity with light circular motions. You are not trying to abrade anything. The soak has already done the chemistry. The scrub is just agitating the loosened residue off the surface. Rinse the sponge and repeat if necessary. Pay attention to corners, edges, and any detail areas where mineral film tends to concentrate.
Step 4: Rinse thoroughly. Rinse the mould under running hot water until the water runs completely clear and the soap is entirely removed. Soap residue left in the mould cavity will transfer to the surface of your next cast and show up as a faint sheen or uneven matte texture. Rinse more than you think you need to.
Step 5: Dry before storage. Shake off the majority of water, then set the mould on a clean dry surface in its natural shape, cavity facing down, for air drying. In Indian conditions during humid months, allow at least two hours for full drying before storage. An electric fan directed at the mould speeds this up significantly. Do not store a damp mould: moisture trapped inside accelerates mould degradation over time and can produce surface marks on the next cast.
Can you use a dishwasher?
Yes, with two conditions. Place the mould cavity-side down so water drains rather than pools. Use a standard dishwasher cycle, not a high-temperature sanitize setting: most silicone moulds handle standard dishwasher heat fine, but prolonged exposure to temperatures above 80 degrees Celsius over many cycles can gradually degrade the silicone surface. If you wash moulds in the dishwasher regularly, inspect them periodically for any tackiness or loss of the natural low-tack surface.
The handwash method above is gentler and more reliable for moulds with fine detail or complex cavities where dishwasher water pressure may not reach every area.
Dealing with pigment staining
If you have been running consistent dark colour pours (black oxide, dark umber, deep red), the silicone may develop a faint tint over time. This is cosmetic and does not affect the mould's function. For light-coloured or white pours, though, a stained mould can transfer a slight discolouration to the new cast.
To address pigment staining, extend the soak time to 60 minutes and add a small amount of white vinegar to the hot soapy water, roughly one tablespoon per litre. The mild acid in the vinegar helps lift mineral and pigment deposits that soap alone does not fully remove. Rinse very thoroughly afterwards since any vinegar residue left in the cavity will affect the surface of the next pour.
For stubborn staining that persists after several cleaning cycles, a short soak in diluted hydrogen peroxide (3 percent, the standard pharmacy concentration) for 15 to 20 minutes can help lift residual pigment. Rinse very well and allow full drying before use.
What not to do
Sharp implements damage silicone permanently. A knife, palette knife edge, or any metal tool dragged across the cavity surface to dislodge a stuck piece creates micro-scratches that catch mineral residue and become progressively worse with each pour. If a piece is stuck, apply gentle outward pressure around the base of the mould to break the seal and allow the piece to release cleanly.
Solvent cleaners, acetone, rubbing alcohol, and spirit-based cleaners degrade silicone over time. They break down the surface polymer and produce a tacky texture that then attracts dust and affects demould performance. Hot soapy water is always the right cleaning solution for silicone.
Storing moulds compressed, folded, or under weight from other objects distorts the cavity over time. Silicone has elastic memory, but repeated compression in the same direction eventually produces a set in that shape. Store moulds in their natural open shape.
Storage for Indian studio conditions
Indian conditions present one specific issue for mould storage: dust. Silicone has a slight natural tackiness that attracts fine dust, and stored open moulds accumulate a dust layer that has to be cleaned out before the next pour. The simplest fix is to store moulds cavity-down on a clean surface or inside a labelled ziplock bag. A clean cotton cloth draped over stored moulds works equally well.
Keep moulds out of direct sunlight during storage. Prolonged UV exposure does not affect silicone chemistry quickly, but it can cause surface discolouration over months of direct sun in the storage area. A shelf away from windows or a covered storage tray is ideal.
The full production workflow, including how mould choice affects demould time and surface finish, is in the beginner guide.
The complete CALSO ONE collection includes silicone mould options alongside the casting material if you are building out your setup.
Frequently asked questions
How often should I clean silicone moulds when using CALSO ONE?
After every session, or at minimum every three to five pours. CALSO ONE leaves a fine mineral film with each use. Cleaning after every session prevents this from building up to the point where it affects surface detail. If you are running light-coloured pours after dark-coloured ones, clean and inspect the mould before the first light cast to avoid pigment transfer.
My silicone mould has a sticky or tacky feel after cleaning. What happened?
Tackiness after cleaning usually means either solvent contact (acetone, alcohol, or spirit-based cleaners) or repeated high-temperature dishwasher cycles have started to degrade the silicone surface. Unfortunately, once silicone develops tackiness from surface degradation, it does not fully recover. Going forward, use only hot soapy water for cleaning and avoid dishwasher sanitize cycles. For mild tackiness, a generous coating of cornstarch or talcum powder on the surface before the next pour can temporarily reduce the effect.
Can I use the same mould for different materials, like CALSO ONE and candle wax?
Yes, but clean thoroughly between material types. Wax residue in a mould used for CALSO ONE will create a waxy spot on the eco resin surface that resists the mineral mix and produces a surface defect. CALSO ONE residue in a wax mould is generally less problematic but still worth removing for a clean release. Full hot water soak and scrub between material types is the standard.
How long do silicone moulds last if properly maintained?
With proper cleaning and storage, a quality silicone mould handles hundreds of pours before showing meaningful degradation. The failure modes are usually edge tears from rough handling, surface scratches from sharp implements, or surface tackiness from solvent exposure. None of these are normal wear from regular CALSO ONE casting. Moulds that are cleaned after each session, stored flat, and never exposed to solvents or sharp tools typically outlast their owners' interest in the specific shape.
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