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I am making a mold for the first time. Do I need a release agent? If yes, which release agent should I use?

Release Agents are a topic unto themselves. Applying no release agent or the wrong release agent can result in your mold rubber bonding or mechanically locking on to your original model.

The type of release agent you choose to release mold rubber from a surface depends on the type of rubber you are using to make your mold and the surface you are releasing it from.

The easiest way to determine the appropriate release agent for your application is to read the mold rubber product technical bulletin available from Smooth-On (many Smooth-On product technical bulletins are available on the Smooth-On website). The TB will tell you exactly what sealer and or release agent to use and under what circumstances you need to use it.

You can use the below charts as a general guide for making molds using urethane rubber or silicone rubber.

When You Are Making a Polyurethane Rubber Mold . . .

And Your Original Model is Made of . . .

Seal It With . . .

Then Apply This Release Agent Before Mixing and Applying Rubber

Modeling Clay - Water Based

Shellac‡ or PVA*


Universal Mold Release or
Ease Release 200**

Modeling Clay - Sulfur Based

Shellac‡ or PVA*


Universal Mold Release or
Ease Release 200**

Modeling Clay - Sulfur Free

Not Required


Universal Mold Release or
Ease Release 200**

Wax

Not Required


Universal Mold Release or
Ease Release 200**

Foam (Polyurethane)

Shellac‡ or PVA*


Universal Mold Release or
Ease Release 200**

Non-Porous Hard Plastics

Not Required


Universal Mold Release or
Ease Release 200**

Wood

SuperSeal, Sonite Wax†
or Shellac‡


Universal Mold Release or
Ease Release 200**

Plaster / Gypsum

SuperSeal, Sonite Wax†
or Shellac‡


Universal Mold Release or
Ease Release 200**

Stone / Concrete / Cement

SuperSeal, Sonite Wax†
or Shellac‡


Universal Mold Release or
Ease Release 200**

 


General Information


1. The above combinations of sealers and release agents are necessary for successfully making rubber molds using Smooth-On PMC®, ReoFlex®, VytaFlex® and Brush-On® rubber mold compounds.

2. *PVA = Polyvinyl Alcohol is an effective sealer/barrier coat, but can be difficult to apply and is recommended only for experienced users.

3. **Use only release agents that are made specifically for mold making. Universal® Mold Release and Mann Ease Release® 200 (spray or brushable forms) are proven and reliable. Both are available from Smooth-On and its distributors. Apply a light mist coating, brush over surface detail, apply second light mist coating and let dry.

4. † Sonite Wax is suitable for sealing a variety of surfaces. It is available from Smooth-On and its distributors.

5. ‡ When using shellac as a sealer, you mush use a high quality spray shellac such as Zinsser Bulls Eye brand spray shellac

6. Porous materials need to be sealed, followed by a release agent before applying mold rubber.

7. Nonporous materials require only a release agent before applying the mold rubber.


When You Are Making a Silicone Rubber Mold . . .

And Your Original Model is Made of . . .

Seal It With . . .

Then Apply This Release Agent Before Mixing and Applying Rubber

Modeling Clay-Water Based

Acrylic Spray†
(optional)


  Ease Release 200 (optional)

Modeling Clay-Sulfur Based*

Acrylic Spray†
(required)


  Ease Release 200 (optional)

Modeling Clay-Sulfur Free

Not Required


  Ease Release 200 (optional)

Wax

Not Required


Not Required
 

Foam (Polyurethane)

Acrylic Spray


 Ease Release 200 (optional)

Non-Porous Hard Plastics

Not Required


Not Required
 

Wood

SuperSeal, Sonite Wax or Acrylic Spray†


  Ease Release 200 (optional)

Plaster / Gypsum

SuperSeal, Sonite Wax or Acrylic Spray†


  Ease Release 200 (optional)

Stone / Concrete / Cement

SuperSeal, Sonite Wax or Acrylic Spray†


  Ease Release 200 (optional)


General Information

1. * Mold Star 15 and Rebound 25 silicone rubbers can not be used on sulfur clay, even if the clay is sealed with clear acrylic.

2. † When using acrylic spray as a sealer, you mush use a high quality acrylic spray such as Krylon Crystal Clear brand acrylic spray.

2. Your best bet is to refer to the specific product technical bulletin for the mold rubber that you are using.

3. The above combinations of sealers and release agents are suggested for successfully making rubber molds using Smooth-On Mold Max®, Smooth-Sil®, Dragon Skin®, EcoFlex®, OOMOO® and other silicone
mold rubbers.

4. Use only sealers or release agents that are compatible with silicone rubber such as Ease Release 200, proven and reliable. Ease Release 200 is available from Smooth-On and its distributors. Apply a light mist coating, brush release over surface detail, apply second list mist coating and let dry.



The FAQ list is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Material Safety Data Sheets (MSDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.



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