Silicone Inquiry with Casco Bay Molding

Casco Bay Molding took special attention in addressing my questions to the fullest.  They included information that I didn’t inquire about but should have.


Andrew, the President and Principal Owner of Casco Bay Molding and I had a lot of correspondence over a few weeks.  He was very helpful, forthcoming and open about the silicone, the process, the company and the team.

He shared so much information that is not included here.  I was happy to share my info and suggestions to his own questions.  I would love to work with Casco Bay Molding in the future if the opportunity arises.

Please note that when I contacted Casco Bay Molding, I did NOT use the name “Red Herring” nor an email that was linked to that name.  I did not want any company to answer questions based on WHO I was.

Andrew Powell – President & Principle Owner of Casco Bay Molding (17 years)

BS, Mechanical Engineering 1984

All in One Facility – Silicone & Plastic Product Development, Manufacturing, and Industrial Automation

Specializing in Medical, Industrial, and Consumer Injection Molded Parts & Products.

The holder of several US Patents

ISO Certified Silicone Rubber & Plastic product development, Design Products, Design Molds, Fabricate Molds, Debug both product design/mold and High Volume Production.

Skills – Injection Molding, Plastics, Product Development, Manufacturing, Molding, Negotiation, International Sales, Rubber, ISO, Product Design, Design for Manufacturing, Solidworks, CAD

The Casco Bay Molding Company is an “all in one” factory – Silicone & Plastic Product Development, Manufacturing and Industrial Automation.  They have also designed and produced their own Menstrual Cup.


You can visit them @ Casco Bay Molding to find out more about them.

Want to purchase the Casco Cup or read more information about it?  Click Here

Use the code “RedHerringTV” for 25% off of your order.

(Contact for orders outside of the USA)

Feb 5, 2017

“Thank you for the penetrating Menstrual Cup Silicone questions!
I will share our responses to the important issues in our FAQ

Please give me a few days to double check a couple of details with my silicone chemist buddies!  You are correct we are a Silicone product development and manufacturing company, we run only Medical-Healthcare grade, Class VI Liquid Silicone Rubber – including the Casco Cup and Casco Case”

Here are the questions that I asked and answers they shared:

Red Herring:  What is Medical Silicone?

Casco Bay Molding: Medical Grade Silicone generally means one of two things confirmed by this Wikipedia link:

  • Medical-Long Term Implantable Silicone designed to stay in the body normally as part of an implantable device. This grade is generally too expensive for Menstrual cups and food grade applications.
  • Medical-Healthcare Grade, Class VI Silicone, tested for Bio-compatibility. Medical Class VI is the material choice for Casco Bay Molding’s Menstrual Cups, Baby Bottle Nipples, food & skin contact, Scuba & Athletic Mouthpieces.

Both Medical-Healthcare Grade, Class VI Silicone and Medical-Long Term Implantable Silicones are considered Food Grade approved FDA.  Both grades are almost always LSR (liquid silicone rubbers) that are normally processed via injection molding.

Red Herring:  What is the difference between Peroxide and Platinum Cure?

Casco Bay Molding: First let’s outline the four major types Silicone commercially available:

LSR– Liquid Silicone Rubber: LSR is designed for injection molding and is almost always Medical Grade Silicone delivered to processors in two sealed drums or 40 lbs. buckets. One drum/bucket has a catalyst, the other has the crosslinker. LSR advantages are that it is pumped directly from the drum/bucket into the molding machine with little to no possibility of modifying the material with the exception of silicone colorant.  Most medical parts are LSR.

HCR– High Consistency Rubber: Premixed, playdough-like that starts with a “base stock” of silicone then a catalyst and fillers/additives are added to silicone base stock on a two-roll mill. Once this step is complete, the HCR is brought to the compression molding press (to make parts) or extruder (to make tubes).

HCR has the advantage of being able to mix in different additives or fillers to change the Silicone’s physical characteristics. This can also be a disadvantage if the additive & filler amounts and ingredients are not shared with the end user. It is also tempting to use extra filler (filler is much cheaper than silicone base) to make more parts with the same amount of silicone-based material. 

Frequently evidence of filler can be seen in wristbands, children’s toys and even menstrual cups that turn white when stretched.  HCR can be a Platinum, Peroxide or Tin cure system, see below for more info on cure systems.

FSR– Fluorosilicone Rubber: flame resistant, brake fluid resistant silicone used mostly in the auto industry.

RTV– Room Temperature Vulcanized Silicone: RTV solidifies or vulcanizes at room temperature. It is used in prototype parts & Silicone caulks fall into this category.

Cure Systems:  Silicones cure (chemical reaction) over time and temperature once a Platinum, Peroxide or Tin catalyst is added to silicone.  LSR & HCR cure relatively quickly once exposed to high heat 350F +/-60F at room temperature it may take days (LSR) or weeks (HCR) to cure.

Three most prevalent silicone curing systems:

  • Platinum Cured: LSR (liquid silicone rubber) is almost always Platinum catalyzed. Properly molded Platinum Menstrual Cups do not need to be post cured. Platinum Cured LSR is generally medical silicone and what we use at Casco Bay Molding.
  • Peroxide Cured: A good deal of HCR Silicone is Peroxide Cured and used for extrusion, transfer or compression molding.  Peroxide cured HCR need to be Post Baked in order to remove the volatiles, this can be a time consuming & expensive step.

If a company tries to cut cost by shortening or cutting the necessary post bake step, volatiles can remain in the silicone. Peroxide cure systems are generally much less expensive than Platinum systems but require a time-consuming post bake.

  • Tin Condensation Cure Systems: Not recommended in healthcare or medical application because the Tin (Sn) remains in the compound after curing.

The information in the next two paragraphs was not part of Casco Bay Molding’s replies.  This info was found through the links at the end of each paragraph.

***More on Peroxide Cured HCR (High Consistency Rubber):

“A serious drawback to the use of peroxide cure in silicone materials is that it leaves residues in the cured elastomer, including acid by-products and polychlorinated biphenyls (PCBs).  If the acid residue is not removed, it can manifest itself as a powder that forms on the part surface –a phenomenon commonly referred to as bloom. The application of an oven cure or post cure cycle is generally required to remove these by-products from the cured parts.” Found here:

“Because of PCBs’ environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants in 2001.[3] The International Research Agency on Cancer (IRAC), rendered PCBs as definite carcinogens in humans. According to the U.S. Environmental Protection Agency (EPA), PCBs cause cancer in animals and are probable human carcinogens.[4] Many rivers and buildings including schools, parks, and other sites are contaminated with PCBs, and there has been contamination of food supplies with the toxins.  Other toxic effects such as endocrine disruption (notably blocking of thyroid system functioning) and neurotoxicity are known.”  Found here:

Red Herring: Why would a silicone turn white when stretched, pulled, twisted, pinched or stressed in any way?

Casco Bay Molding: Fillers are less expensive than Medical silicone.  HCR (High Consistency Rubber) is frequently loaded with filler that does turn white when pulled.

However stiffer durometers (60, 70 and 80 Durometer) has some amount filler required to stiffen the material.  Generally, this is still not noticeable when stretching LSR parts.

Red Herring: Is Vulcanized Compression Molding the best?  Why or why not?  Do you feel another process is superior to this one?

Casco Bay Molding:  Vulcanization is a chemical process for natural rubber and man-made silicone.  For both LSR and HCR the silicone processor should not try to mix in an extra filler.  The compound should be used as received.

Different part manufacturing methods (compression, transfer, injection) should be selected on a cost vs. performance basis.  In our opinion, Menstrual Cups are best produced with as few volatiles and smallest amount unknown fillers and additives (Platinum LSR).  We believe strongly in full material traceability the same procedures we use for medical device component manufacturing.

With Peroxide cure HCR, the extra filler should not be added and a proper post bake should be conducted to remove all volatiles.

Red Herring: Some companies suggest boiling a menstrual cup to sanitize it, while others suggest against it.  I was under the impression that a silicone (Food and/or Medical grade) were created to withstand high temperatures for cooking and/or use in an autoclave.  Do you have any thoughts about silicone and high heat?

Casco Bay Molding: We strongly recommend boiling your cups for sanitation, especially for people in nations where clean water is an issue.  We also recommend boiling our Casco Case made from Medical Silicone and plastic.

Westerners have the luxury of using sanitary wipes, clean damp paper towels or their sink when changing their cup during menstruation.

Real silicone has no issue with boiling water.  We do not recommend a hot griddle or frying pan because the temperature is hard to monitor.  Over 400F may cause discoloration but may not change physical properties of the silicone. Silicone is flammable; it should never be exposed to an open flame.

Red HerringAnother path my search took me, was through silicone sex toys.  People have claimed that they “test” their toys by doing the “ash test”.  This is the process of burning a good portion of the silicone item to see the outcome.  They claim that a Medical Grade Silicone will not continue to flame, will not melt, and will leave behind a pale gray ash and show no or minimal signs of damage. 

Casco Bay Molding:  The Ash Test is a plastics laboratory test to check for volatiles in the plastic.  There was a difference of opinion on silicone.  For any skin contact or short term-internal body application, we recommend Platinum cured Medical grade ClassVI Silicone.

Red HerringOne more thing that came up on the sex toy sites is that “pure silicone will never be crystal clear and see-through. The extreme stretch and the jelly look of the material means it’s not silicone”.

Casco Bay Molding:  Not necessarily true, silicones can have very high elasticity.

Regarding clear silicone, with the advent of LED lights, there are a few optical grade silicones on the market. With injection molding grade LSRs, mold surface finish has a lot to do with how translucent the Menstrual Cup appears.  The Casco Cup has a slight texture for a frosted look, while we polished the soft tip of the M-Cup.  HCR generally is less translucent, especially if the use fillers.

Sex toys are relatively unregulated, not a lot of material certifications or traceability.

Red HerringWith Menstrual Cups becoming more popular all over the world, there have been a lot of cups being made that are questionable.  Some are very thin or flimsy.  Several are even too soft to seem usable.  I don’t doubt that some are made with lesser silicone/materials or “fluffed” with undesired fillers to cut the cost of making them, but how are we to know?

Casco Bay Molding:  We could not agree more which is why we see a place for ourselves in the menstrual cup market.  We want to assist people here and in developing nations around the world with a safe Menstrual Cup they can trust.

Our cup was primarily designed by two people, Liz at Casco Bay Molding with input from Chelsey of Green Cup of Maine.  We spent a lot of effort finding the right combination of part thicknesses, overall design, and proper material selection.

Our cup is FDA Registered, has full material traceability, is Platinum cured, Medical Class VI Liquid Silicone Rubber, produced in an ISO Certified factory, sold factory direct to consumers, US stores, NGOs, foreign distribution partners. We also private label cups for other companies under the same manufacturing and quality conditions.

Red Herring:  We are inserting these items into our bodies for long periods of time.  My concern is for my health and safety as well as others that use these products, including my own daughter and nieces.

Casco Bay Molding: I/we could not agree more! My partner, friends, colleagues, and daughter use our cup. We/I want it to have a superior design, produced from the best material possible made by people who care!

***  Casco Bay Molding Note:  The information above was in response to a series of questions I received from a truly independent Menstrual Cup expert.  I discussed these question with three trusted silicone Chemist, I have known for years.  The Chemists have worked all worked for decades at least two Silicone Manufacturers including Momentive/GE, Wacker, Dow Corning and Blue Star.

Silicone Inquiry with Wacker Chemical Corporation

Silicone inquiry with SSPInc.

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