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

Soapmaking Forum - Soap & Candle Forums

Help Support Soapmaking Forum - Soap & Candle Forums:

AustinStraight

Well-Known Member
Joined
Mar 14, 2014
Messages
291
Reaction score
114
Location
New York
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?
 
Last edited:

Rowan

Well-Known Member
Joined
Feb 10, 2014
Messages
833
Reaction score
522
Location
UK
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

Well-Known Member
Joined
Sep 14, 2015
Messages
259
Reaction score
319
Location
California
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

Well-Known Member
Joined
Oct 7, 2015
Messages
89
Reaction score
83
Location
Berlin, Germany
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

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
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

Supporting Member
Joined
Jan 14, 2015
Messages
1,906
Reaction score
2,081
Location
Monroe, LA
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.
 

kchaystack

Supporting Member
Joined
Jan 14, 2015
Messages
1,906
Reaction score
2,081
Location
Monroe, LA
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

Supporting Member
Joined
Sep 29, 2015
Messages
3,497
Reaction score
2,642
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

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
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:
 
Top