Wednesday, February 2, 2011

DIY Silicone Liners for Soap Moulds

I was fortunate enough to stumble upon Tortuga Soaps and find Kaseen Cook's great website. She has two tutorials along with other information about saving turtles (we love turtles!): one on how to make your own silicone liner for soap molds.

Kaseen gave me permission to share this project with you (thank you, Kaseen!!)


You can make your own silicone liners for your soap moulds; all you need is some RTV silicone (easily sourced from the internet or locally) and some simple supplies you can usually find around the house. Silicone is not a cheap material, so making your own can save you labor cost, as well as make soaping easier and more fun without having to line your moulds all the time! You can also pour your liners onto cool textures to make all sorts of uniquely textured soaps. Try pouring on engraved plaster to create a liner custom made with your logo. It takes a bit of patience, but is certainly not too hard for anyone to accomplish in a weekend. Silicone is the only material that will adhere to silicone. It does not “glue” the pieces together, it chemically welds them, which means that when joining two pieces of silicone with silicone they become chemically and physically the same object. This is like metal welding, only with silicone, so the finished product is just as strong as one that was made with one pour. There isn’t much difference to the end user having a liner made in one pour vs. one welded from pieces, although they take longer to make, but as long as the pieced one is put together with care and attention to detail, they are just as good. Welded silicone liners are strong and practical for those wanting to make liners and save some money. **For even cheaper liners, you could try Polyurethane Rubber. Polyurethane is not “self-releasing” like silicone, so will require mould release agents like food grade silicone and wax, but savings of up to 50% off the cost of silicone can be realized. The pros for this material are it’s much cheaper than silicone, firm but flexible material, and very durable and much longer lasting than silicone. The cons are that when molding soap the mould will need a release agent like food grade silicone or wax, so it’s a bit more work than silicone.


Planning the layout –

Measure the length, width and height of your liner, and then arrange into one or two flat areas as in the diagram. Remember, silicone is expensive, measure twice and pour/cut once!

Determining the amount of silicone for your mould – I would suggest a liner thickness of 3mm for the most cost effective use of your silicone as well as not taking up too much space in your mould, while retaining adequate strength. After you have determined the surface area you will need to cover with silicone (the internal surface area), ensure the measurements are in cm, and determine the total surface area in cm squared. If you want a 0.3cm thick mould (3mm), multiply the surface area by the thickness of the liner to get the volume of silicone in cm cubed, or cc’s, or ml’s. This volume is equivalent to the material in weight (as 1cc/ml of silicone is approximately 1g of silicone), so for measurement purposes convert the volume to weight.

Here is an example to illustrate:

Liner surface area (as contained in the frame) is 39x32cm = 1,248cm2 1,248cm2 x 0.3cm(thick) = 374.4ml (or cc’s) = 375g silicone. With the average cost of silicone at $0.05/g = $18.75 As you can see increasing the thickness will greatly increase the price of the liner:

1,248cm2 x 0.5cm(thick) = 624ml (or cc’s) = 624g silicone. = $31.20 1,248cm2 x 1cm(thick) = 1,248ml (or cc’s) = 1,248g silicone. = $62.40 Materials:

· Long wooden battens or strips of cardboard or any other straight objects to make frames.

· Stirring stick/spatula, plastic tub, and gloves.

· RTV Silicone (I would suggest starting with about 1kg for cost effectiveness and for just enough volume without huge investment. If you plan to make many liners or if you have large liners, 5kg packages are the most economical and cost effective of the smaller packages, ranging from $200 to $250AUD)

Desirable properties (guide only):

Low to medium viscosity (45,000 cps or less) for smooth pouring, medium cure time (min about 6 hours to full cure and 30min pot life to allow working time, real cure time is usually half of advertised cure time), and Shore A hardness of 25 or greater – the firmer the silicone (Shore A of 35-50) the thinner the liner can be while retaining the same strength and support (as long as the other qualities are still present).

Australian Resources and Suggestions:

Online –

Adelaide Moulding and Casting


Suggestions: (made by Barnes Silicone)

Maximould, M4503, Ultrasil.

Barnes Silicone ( Suggestions: Use caution if you choose to use Pinky Silicone, as this silicone must be molded in about 6minutes, which may not be enough time to pour/spread your liner, otherwise it’s the best silicone so may be worth a try! Tufsil 25, Maximould, M4503, Ultrasil.

Solid Solutions


Suggestions (Tin Catalysed): Solid Mould 500, Polytek TinSil 70-30.

Local –

Check your local Fiberglass and Mould Making Supplies Store; many carry RTV silicone and the Barnes range of products (their website lists stores that supply their silicone). Just look up “fiberglass” or “molding and casting” in the yellow pages.


1. Layout the batons into the surface area rectangles required for your size liner, to contain/mould the silicone. Be sure to use a right angle tool or the corner of a sheet of paper to square your frame.

2. Tape around the edges of your walls to prevent any silicone leaking out.

3. Ensure the surface you are pouring onto is clean. You can pour onto any surface, including cool textures (bubble wrap, sandpaper, needle point grid, ect.. beware of fabrics or carpet, silicone can soak in and be hard to get out!).

Tips: You can use the side of the silicone that is touching the surface as the inner or outer part of your liner depending on which you prefer. Sometimes it is better to pour your liner onto a slightly textured surface like paper or MDF and use the side that contacts the MDF or paper as the outer side of your liner, because it will not grip onto your outer wooden mould when inserting.

4. Mix your silicone as per the manufactures guidelines (search for pouring silicone and the “bombs away” method on the internet for some really good videos. Tap Plastics makes great instructional videos). Pour into your frame using the “bombs away” method to reduce air bubbles. The bombs away method is essentially pouring a very thin stream from a height to stretch and pop any bubbles that were trapped in the silicone during mixing. Using a plastic spatula spread the silicone into the corners and even-out thin or thick areas.

5. Blow across the silicone with a hair drier set to cool and with an air funnel/straightening attachment to make a concentrated blast, or just blow across the top of the silicone with your mouth, to pop any remaining bubbles (just be careful not to accidentally spit on it or hyperventilate lol).

6. Cover your frame with a board or other stiff cover if you are worried about lint or pets/kids getting into it while it hardens. Allow curing for the recommended time, heat generally speeds up the cure (as the reaction is endothermic), so a blast with a hair drier, heater or keeping it in a warn room will quicken the process. Do not use a heat gun or flame on the silicone, as this is TOO hot. To clean up your mix pot and spoon, just let the silicone cure and peal off, it’s really easy to clean! Or you can put the silicone pot with the extra silicone on the sides in the freezer to prevent it from curing for about 1-2 days, and use it later to join/weld your liner sides.

7. When dry, peal off the frame and surface. Trim/slice the silicone sides to fit into your mould.

8. Mix a small batch of silicone (about 10g is enough) or get the remainder you saved from the freezer and apply to the edges of your liner sides and weld together supported inside your wooden mould (you may need blocks or other objects to hold your sides up from the inside as well). Wipe away excess, and allow curing.

You’re done!


Thank you, Kaseen!

I don't know about you, but if I could have my way, I'd love to have Upland silicone molds for all of my molds because I HATE lining molds with freezer paper. BUT! I found this fantastic do it yourself silicone molding tutorial that you could try.

If you do, please send me pictures!! :)


innerearthsoaps said...

Kaseen is fabulous ... she made my custom soap moulds for me!

Joanna said...

That's awesome, Erin!

Wish I knew about her before she "retired".

Wealth of knowledge.

Michelle @ TheBarOf said...

I found this on their website awhile back, Have been constantly thinking, as having such an awesome cost effect mold that is little fuss. OMG Heaven. But the initial mess with a 3 year old underfoot.
Still dreaming.. But I agree with you they look to be such a godsent project.
Love your blog, BTW

Soapchick said...

That is such a brilliant idea! got to try it!! on web looking for silicone now. perhaps I will photo it for a Naturally Made Soaps blog project!! Ha ha, its bound to go wrong then. thanks for posting this.