Using PVC as a mold....having a few issues with it

[Piero]

Hello people,
Today two posts

After some squared soaps, we decided to try to do some round soaps using the below PVC pipe.

We did not have any real problems when we did batches of 500 grams of soap since we were using another pipe to push the soap out. It was not really easy, but we somehow managed. However, a few weeks back we did one kilo and when trying to push we sort of screwed up some things ruining some parts our soap and having to rethink the whole way we are getting it out.

I am just wondering, how do you get the soap out from the mold?

I have seen videos of people that put it in the freezer for 30 min (we did that) and then they gently slam it on the concrete/ground and it comes out like magic. We have tried that, but we have noticed that not much was moving and sometimes nothing happened, plus we are afraid when using some brutal force to destroy our PVC pipe.

Are there some tricks we are missing?

I am looking forward to hearing from more experienced Soapers !

Have a nice weekend everyone

 

[jcandleattic]

How long are you leaving it in the pipe before freezing? You may have a softer batch that will need more time to harden up before trying to freeze.

Is the soap trying to be pushed past that bump? (that would be hard to push out unless you are pushing from the top to bottom and it's coming out of the bigger hole)

I've used my PVC enough that it's seasoned enough that once it's saponified and hardened it slips right out. However when I make a batch using oils that result in a softer batch I sometimes have to wait a few hours longer, then put it in the freezer and push it out.
I've never had to slam it on the concrete. That sounds extreme...

 

[Ford]

Had you thought about lining? Some people use plastic, some freezer paper. Freezing and banging on concrete seems harsh for an innocent piece of soap.

 

[Piero]

How long are you leaving it in the pipe before freezing? You may have a softer batch that will need more time to harden up before trying to freeze.

Is the soap trying to be pushed past that bump? (that would be hard to push out unless you are pushing from the top to bottom and it's coming out of the bigger hole)

I've used my PVC enough that it's seasoned enough that once it's saponified and hardened it slips right out. However when I make a batch using oils that result in a softer batch I sometimes have to wait a few hours longer, then put it in the freezer and push it out.
I've never had to slam it on the concrete. That sounds extreme...

We are keeping our soap inside the PVC for a week.

The bump is the bottom part, we push from the top towards the bump yes

Had you thought about lining? Some people use plastic, some freezer paper. Freezing and banging on concrete seems harsh for an innocent piece of soap.

I cannot find freezer paper where I live (Italy+Denmark), I know a lot of people are using it and it looks amazing.
As plastic, what do you mean exactly?

Thanks again.

Freezer paper is just a thinner version of "Butcher's Paper". Shiny side towards soap. Thin plastic mats, like cheap place mats for dinner table. there is quite a long post on this subject. "Cylinder PVC molds".

Ok, will look into this opportunity of either buying butcher's paper or plastic mats

Thanks for the tips

My questions and suggestions:

1. I agree with @jcandleattic that you may need to freeze it for longer than 30 minutes. I usually do 1-2 hours minimum.

2. Are you letting the soap cool off and firm up before you put it in the freezer? If not, then the edges will quickly go soft again when you take it out, and soft soap edges don't release easily from the mold.

3. When you take the mold out of the freezer, let it sit at room temp for at least ten minutes to let the condensation build up. Condensation allows the soap to slide more easily.

4. This is my personal theory, and perhaps those with engineering background can correct me if I'm wrong. But I believe that the non-uniform shape of your mold is contributing to the difficulty of release. We see this more dramatically in very detailed molds, where it can be so hard to get the soap to release cleanly. Yours is not detailed, but it does change direction and size. I would be willing to wager a small amount that a straight tube would always release more easily than one that is in the shape of your existing one.

1. We read that 30 minutes was more or less enough, we will keep it longer and then report. Thanks for the tip
2. What do you mean exactly by your question? (sorry we are kind of noobs in the soap making part and not sure what you mean )
3. I believe we did, without actually noticing it. This Sunday we will make a new batch and we will make sure to keep that in mind when we take it out.
4. I will leave this to the experts since it is not my field of study or my background

 

[Ford]

Freezer paper is just a thinner version of "Butcher's Paper". Shiny side towards soap. Thin plastic mats, like cheap place mats for dinner table. there is quite a long post on this subject. "Cylinder PVC molds".

mmm, a week is kind of a long time.

don't know much about soap (still a newbie myself) but I do know my way around a piece of pvc.

 

[GGMA0317]

Had you thought about lining? Some people use plastic, some freezer paper. Freezing and banging on concrete seems harsh for an innocent piece of soap.

 

[AliOop]

My questions and suggestions:

1. I agree with @jcandleattic that you may need to freeze it for longer than 30 minutes. I usually do 1-2 hours minimum.

2. Are you letting the soap cool off and firm up before you put it in the freezer? If not, then the edges will quickly go soft again when you take it out, and soft soap edges don't release easily from the mold.

3. When you take the mold out of the freezer, let it sit at room temp for at least ten minutes to let the condensation build up. Condensation allows the soap to slide more easily.

4. This is my personal theory, and perhaps those with engineering background can correct me if I'm wrong. But I believe that the non-uniform shape of your mold is contributing to the difficulty of release. We see this more dramatically in very detailed molds, where it can be so hard to get the soap to release cleanly. Yours is not detailed, but it does change direction and size. I would be willing to wager a small amount that a straight tube would always release more easily than one that is in the shape of your existing one.

 

[Ford]

Cutting the bell/flare off would take one variable out of the equation. Also makes a shorter pipe. My pvc molds are 12" long. It takes 30oz oil the fill the mold, just below top. (preferred) makes 9, 1 1/8 inch thick bars. I cannot see wanting to go any longer. I have 6 of these.

 

[Piero]

What are you using to close the pipe?
The pipe I found here in Denmark comes also with a cap (this is why it has the bell/flare). We bought this one because according to our calculations it can do both 500gr and 1kg.
We remembered how to calculate the volume of a cylinder and chose this one. Once I go back to my parents place I will try to see if I can find some fully straight pipes with a cap.

 

[Ford]

I have never capped the top. And believe I read somewhere it should not be. If you decide to try lining. Leave a little sticking out the top. (I used .75)
to grab on to. But not to much to be in your way.

 

[AliOop]

2. What do you mean exactly by your question? (sorry we are kind of noobs in the soap making part and not sure what you mean )

No apologies needed! We are all here to help one another.

What I am asking is whether you let the soap batter become firm before putting it into the freezer. If you are pouring it into the mold, then putting it straight into the the freezer, it's not going to release as cleanly because the soap itself didn't firm up first (especially if you are only freezing it for 30 minutes).

As a very general average, many recipes take about 24 hours to firm up. Recipes that are high in CO firm up much more quickly; recipes high in soft oils can take several days. This can also vary depending on the heat of your batter when you pour, and how much more it heats up after you pour.

So how do you know when your soap in a cylindrical mold is firm? The mold should be room temperature when you touch it. When you remove the cap and touch the soap, it shouldn't have much give to it. In other words, it should feel like it is ready to cut.

Hope that helps!

 

[Obsidian]

I coat the inside with a very thin layer of vaseline or mineral oil. Helps the soap slide out with only a little pushing.

 

[Piero]

I have never capped the top. And believe I read somewhere it should not be. If you decide to try lining. Leave a little sticking out the top. (I used .75)
to grab on to. But not to much to be in your way.

I think I realized that what I wrote could have been misinterpreted. I meant on the bottom not on the top

No apologies needed! We are all here to help one another.

What I am asking is whether you let the soap batter become firm before putting it into the freezer. If you are pouring it into the mold, then putting it straight into the the freezer, it's not going to release as cleanly because the soap itself didn't firm up first (especially if you are only freezing it for 30 minutes).

As a very general average, many recipes take about 24 hours to firm up. Recipes that are high in CO firm up much more quickly; recipes high in soft oils can take several days. This can also vary depending on the heat of your batter when you pour, and how much more it heats up after you pour.

So how do you know when your soap in a cylindrical mold is firm? The mold should be room temperature when you touch it. When you remove the cap and touch the soap, it shouldn't have much give to it. In other words, it should feel like it is ready to cut.

Hope that helps!

Oh ok
We pour the soap and wait for it to become hard. After approx a week, we put it in the freezer for around 30mins and then try to take it out. We do wait for it to become firm, yes

Thanks again, will try it next time for sure.

I coat the inside with a very thin layer of vaseline or mineral oil. Helps the soap slide out with only a little pushing.

Thanks for the tip. Aren't the added ingredients going to change the organoleptic properties of the soap?

 

[Obsidian]

Not really. Its such a tiny amount, I've never noticed it changing the soap and after a couple uses, it will be gone.

 

[Mobjack Bay]

Is your recipe high in soft oils? Most soap recipes are ready to cut in 18-48 hours.

I used a very thin layer of mineral oil to help with release from a plastic soap mold I used earlier this year. The soaps came out fairly easily, despite an intricate design. The mineral oil doesn’t saponify and I was worried that the soap would look greasy or have a film, but it didn’t.

 

[AliOop]

I agree with the others that waiting a week is probably too long. Even if your recipe is mostly soft oils, two days would be the max I’d leave it, unless the top is still very soft when you press into it.

 

[mtinetti61]

I used to use PVC pipes and downspouts as molds. Haven't for a long time since I got my silicone ones. Here's the process I used: A thin layer of mineral oil or vaseline; after 48 hours put in the freezer for at least 2 hours (sometimes I'd forget about it and it would be in there way longer but that didn't seem to harm it). Then run under hot water for about a minute (or more depending on the thickness of the PVC). Once in awhile I'd have to bang it a couple of times on the counter top but not hard. Then used a long piece of wood as a pusher. Stand the pusher upright in the sink or on the counter, then push the soap hard down onto it. Eventually the soap would come out nicely.

 

[Rsapienza]

I'm one of the whackers. Any time I've used PVC, I wait about a day, take it outside, and whack the hell out of it on the concrete. It slides right out.

 

[CatahoulaBubble]

I line it with a silicone baking mat.

 

[bonnyny]

I'm one of the whackers too. Line the 3" pvc with a little olive oil before filling with soap. Leave overnight. Smack it on the ground. Sometimes it slides right out. If it doesn't, then a 2" pvc with a cover pushes it through.