Condensation vs Addition Cured Silicone Moulds
During our research into which is the most suitable material to manufacture our new moulds from, we started to realise that Condensation/Tin Cured Silicones that other mold/mould manufacturers seem to use are not actually recommended for most of the resins that Pen Turners use for clear casting.
We're not trying to tell you which moulds you should use for your Pen Blank casting as despite all these warnings it looks like pen turners have been using & getting away with the Condensation/Tin Cure for years. We just wanted to let you know about this information so that you can make your own decision. We are manufacturing both Condensation Cured and Addition Cured Moulds so when purchasing moulds from our website you will have the option of choosing either.
The two Silicones we use for making our moulds are:
Condensation Cure RTV (Light Pink) - catalyzed using tin salts hence why its also referred to as Tin Cure.
Addition Cure RTV (Dark Pink) - catalyzed using platinum so sometimes referred to a Platinum Cure.
(RTV means Room Temperature Vulcanization)
Both of these types of silicone are very different from each other. More importantly, they are not compatible with one another either.
Our Condensation Cured Silicone Moulds:
Colour - Light Pink
Tear Strength - 23
High elasticity for easy removal of complex replica parts
Outstanding release properties
Short Library Life (meaning approximately 5 year shelf life)
Our Addition Cured Silicone:
Colour - Dark Pink
Tear Strength - 22
Outstanding release properties
Long Library Life (meaning approximately 20 year shelf life)
Please Note:
When purchasing your mould that most of the manufacturers state that Condensation Cured Silicone Moulds should not be used with Water Clear Polyurethanes as this will inhibit the cure and Addition Cured Silicone Moulds should be used instead. Some manufacturers also state that Condensation Cured Moulds should not be used with their Clear Polyester Resins or Clear Epoxy Resins again as they inhibit cure and again recommend an Addition Cured Silicone Mould is used instead.
Snippets taken from some of the main Supplier's Technical Data/Instruction Sheets
POLYURETHANE RESINS
Alumilite Clear and Water Clear
It is best to use platinum base silicone rubber molds when pouring Alumilite Clear and Water Clear. New tin base silicone rubber molds should be conditioned to clean and crosslink any uncured tin that is on the surface of the mold that may contaminate the clear casting.
Water Clear Polyurethane Casting Resin
Condensation cured silicone rubber should not be used with this casting resin.
Polycraft Opti-Cast 100
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
Polycraft FC‐6600 Slow Set Water Clear
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
Polycraft FC‐6666 Doming Resin
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
EPOXY RESINS
GlassCast Clear Epoxy Surface Resin
GlassCast® should not be cast into Condensation/tin cure RTV silicone rubber moulds.
POLYESTER RESINS
Water Clear Polyester Casting Resin
Both of our types of silicone could be used but generally you'll get better results when casting water clear resins (polyurethane or polyester) by using an Addition Cure Silicone Rubber.
We're not trying to tell you which moulds you should use for your Pen Blank casting as despite all these warnings it looks like pen turners have been using & getting away with the Condensation/Tin Cure for years. We just wanted to let you know about this information so that you can make your own decision. We are manufacturing both Condensation Cured and Addition Cured Moulds so when purchasing moulds from our website you will have the option of choosing either.
The two Silicones we use for making our moulds are:
Condensation Cure RTV (Light Pink) - catalyzed using tin salts hence why its also referred to as Tin Cure.
Addition Cure RTV (Dark Pink) - catalyzed using platinum so sometimes referred to a Platinum Cure.
(RTV means Room Temperature Vulcanization)
Both of these types of silicone are very different from each other. More importantly, they are not compatible with one another either.
Our Condensation Cured Silicone Moulds:
Colour - Light Pink
Tear Strength - 23
High elasticity for easy removal of complex replica parts
Outstanding release properties
Short Library Life (meaning approximately 5 year shelf life)
Our Addition Cured Silicone:
Colour - Dark Pink
Tear Strength - 22
Outstanding release properties
Long Library Life (meaning approximately 20 year shelf life)
Please Note:
When purchasing your mould that most of the manufacturers state that Condensation Cured Silicone Moulds should not be used with Water Clear Polyurethanes as this will inhibit the cure and Addition Cured Silicone Moulds should be used instead. Some manufacturers also state that Condensation Cured Moulds should not be used with their Clear Polyester Resins or Clear Epoxy Resins again as they inhibit cure and again recommend an Addition Cured Silicone Mould is used instead.
Snippets taken from some of the main Supplier's Technical Data/Instruction Sheets
POLYURETHANE RESINS
Alumilite Clear and Water Clear
It is best to use platinum base silicone rubber molds when pouring Alumilite Clear and Water Clear. New tin base silicone rubber molds should be conditioned to clean and crosslink any uncured tin that is on the surface of the mold that may contaminate the clear casting.
Water Clear Polyurethane Casting Resin
Condensation cured silicone rubber should not be used with this casting resin.
Polycraft Opti-Cast 100
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
Polycraft FC‐6600 Slow Set Water Clear
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
Polycraft FC‐6666 Doming Resin
Do not use this resin in moulds made from condensation cure silicones as this will inhibit the cure.
EPOXY RESINS
GlassCast Clear Epoxy Surface Resin
GlassCast® should not be cast into Condensation/tin cure RTV silicone rubber moulds.
POLYESTER RESINS
Water Clear Polyester Casting Resin
Both of our types of silicone could be used but generally you'll get better results when casting water clear resins (polyurethane or polyester) by using an Addition Cure Silicone Rubber.