Bath Bomb Guide to different types of moulds
It can be very confusing when you start out to try and work out what moulds you need. There are so many fantastic designs and also materials to choose from. While it is tempting to just buy as many as you can (we have all been there) one of the better ways is to understand the material that is being used and which to buy that will bring you the highest chance of success.
I wanted to break this into a pro and con list as there is no definitive top 3 type of list. This really comes down to how you find that you use moulds (some like to bang them, scrub them, use them for a range of products etc) I will list them as I find the most logical with respect to bath bombs and from a beginner level to advanced type.
Metal
These, in general, are made up of Aluminium, they are lightweight and can also sometimes be listed as small cake/dessert moulds also. There are not a lot of custom small businesses that produce these as they need large machines to make. That being said there are some great cute designs to find around the place and new designs to pop up.
Pro
You can bang these around and get a bit rough with them and they are okay. They don't scratch easily and tend to have lovely smooth rounded designs that easily pop out bath bombs. They are quite cheap (unless you happen to find Stainless steel however even these are still an affordable price)
Cons
You can dent them (if you bang them in the wrong spot) and if they are dented they are hard to fix. With the Aluminium they can eventually rust if you do not keep them dry, they do not have a coating on them that will protect them.
Plastics
There are many types of plastics on the market, this has to do with the versatility of the material. Many small businesses can make their own plastic shapes so the design area of these is immense! This is thermoforming plastic which is to say it is heated up over 130 degrees and then bent into shape. While there are many types we will touch on the most common ones used.
Plastic HDPE
High Density Polyethylene this comes in two forms thick solid white plastic that is used for soap slab moulds or thin clear plastic normally for bath bombs.
Pro
Many different shapes out there use this material. It is relatively cheap and easy to ship. This is also a food grade plastic so as well as bath bombs it could be used for chocolate, jellies, ice cubes, etc. It is the same plastic your water bottles are made out of so can be recycled through your collection bins easily.
Cons
These can be scratched and once scratched the bath bomb mixture will stick to it every time. This more rigid type of plastic is also prone to cracking/shattering if left in sunlight accidentally over time.
Plastic LDPE
Low-Density Polyethylene is also a thermoforming plastic which many use. This is characterised by a milky or cloudy type look in pictures.
Pro
This is a thicker and flexible type of plastic and a go-to for many. Because of its thickness, it is less breakable and the softer type lends itself to being able to ‘squish’ your mix around while inside the mould a bit better. This can also be recycled easily.
Cons
These can also be scratched and the bath bomb mix will stick to any scratches. As the name suggests with Low Density these can absorb, discolour over time however this does not affect the performance of the item.
Plastic PETG
Polyethylene Terephthalate is another food-grade and widely used plastic. This is a thin clear plastic that is also thermoforming.
Pro
Many different shapes out there use this material. It is relatively cheap and easy to ship. This is also a food grade plastic so as well as bath bombs it could be used for chocolate, jellies, ice cubes, etc. It is the same plastic your water bottles are made out of so can be recycled through your collection bins easily.
Cons
These can be scratched and once scratched the bath bomb mixture will stick to it every time.
3d Printed Bath Bomb Moulds
These are commonly called hand press moulds and are printed with many layers on a printer.
They are printed thick so you can bang and bash them without problems. They are one of the few types that can produce 3d shapes and there are many small businesses producing these which leads to lots of great designs. These typically use a plastic called PLA. I would consider these an intermediate style as they take some learning however they are a great fun project to do.
These can be more expensive in comparison to other moulds due to the time they take to produce. They also can warp with heat damage if put through the dishwasher or a hot car. They can also come apart in the layers if there is water left in them. Normal use of these however will set you up with a solid great piece of equipment.
Silicone
Available in all different colours these are cheap and readily available.
Pro
These hold up well to outside conditions and are very versatile. These can be used for many other projects also such as bubble bars, wax, soap, etc
Cons
These do not offer the rigidity needed to press the bomb mix into the mould (as they will just bend) so you can press these in and let the mix dry inside the moulds. This means you cannot produce one and unmould quickly. This means they are better suited for smaller projects or one-off makes.