Is it safe to use a plastic water bottle as a mold?

[AustinStraight]

I usually use a silicone loaf mold or parchment paper-lined stainless steel pans for safety & ease of cleanup, but I just realized one of my dad's (overpriced) mineral water bottles would be the perfect size to use as a cylinder mold... buuut I don't know if it's safe. I've seen similar bottles used as molds for melt & pour but never cold process, would it melt the plastic? Can anyone speak from experience?

 

[Rowan]

Sorry, I can't say whether a plastic water bottle would hold up or not, as I've not tried it. However I have used plastic yoghurt cartons, which have been totally fine. If you freeze it for a short time before cutting the soap comes out really easily.

If you're looking for other ideas for cylinder moulds, you can also use plastic pipes from DIY stores. They're a little bit difficult to unmould. I cut mine too long at first and they didn't fit in the freezer! You could also try a Pringles can for cylinder moulds.

 

[annalee2003]

I think the plastic has to have a (recycled?) number on it somewhere that is either a 2 or 5. I'm not 100% sure though, expert soapers please chime in!

 

[notapantsday]

Somehow the 4 is always forgotten, that one's fine too.

Water bottles are usually made from PET though (1). PET is not as chemically stable as HDPE (2), LDPE (4) or PP (5) and sensitive to lye. I wouldn't use it.

In the end, the single PET monomers are connected by the same type of bond as the glycerin and the fatty acids in our oils (no, you can't make soap from PET bottles).

 

[Spice]

Sorry, I can't say whether a plastic water bottle would hold up or not, as I've not tried it. However I have used plastic yoghurt cartons, which have been totally fine. If you freeze it for a short time before cutting the soap comes out really easily.

If you're looking for other ideas for cylinder moulds, you can also use plastic pipes from DIY stores. They're a little bit difficult to unmould. I cut mine too long at first and they didn't fit in the freezer! You could also try a Pringles can for cylinder moulds.

How do I line a Pringles can? I thought that at the end there is a metal tap?

 

[kchaystack]

Cut off the metal end and use the plastic lid as the bottom. Put some tape around it to keep it secure.

I also put a sheet of parchment rolled into a tube to line the sides so I can pull the soap out and reuse the can a few times.

 

[dixiedragon]

Isn't the inside of the can foil? I assume that's why you have to line it?

 

[kchaystack]

Isn't the inside of the can foil? I assume that's why you have to line it?

In the US at least, the foil is covered by a thin layer of food grade plastic. So it does not need to be lined. But if you don't the only way to get it out is to peel the tube off.

 

[Arimara]

I would suggest against a plastic water bottle. They can barely stand hot brewed tea without morphing. There's not way that a water bottle's going to tolerate being a mold for a soap. Ideally, you would want to use type 2 or 5 at least, as others have suggested. I plan on using a now empty lye container as a mold once I decide on how to convert it.

 

[Spice]

Cut off the metal end and use the plastic lid as the bottom. Put some tape around it to keep it secure.

I also put a sheet of parchment rolled into a tube to line the sides so I can pull the soap out and reuse the can a few times.

interesting. I will be getting some pringles.
:neutral: