Silicone release from form

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micharms

micharms

Member
Joined
Nov 8, 2004
Messages
681
Location
Port Elgin, Ontario, Canada.
I've decided to try pouring my own bottlestoppers molds. I have some Mold Max on order. My form will be dowels and plywood or corian walls and base. I'm going to seal the dowel and plywood (if used) with Vaseline and mineral spirit mix. What else do I need to do to ensure that the silicone will release from the form?

Thanks
Michael
 
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You'll need access to a compressor to make it easier. You can do it
without one, but it's more difficult.
Your release will work fine, but there's a tight seal in the mold with the
stopper holding out the air. You'll need to get air in behind the stopper
for it to come out easily. You could stick something down the side of
the stopper to release the vacuum, but it is easier to blast some air
down the side. The stopper will then pop out.
You could probably do it with canned air, too but that's pricey.
GO easy with the compressor .. it will launch the stopper.

DAMHIKT :tongue:
 
Thanks Charlie. I was hoping you'd respond. I had heard of using the blast of air to get the stoppers out after casting but I am glad you warned me about going easy with the compressor.

What I am more concerned about is getting the mold to release from my plywood and dowel form that I am using to create the mold. Is the Vaseline/mineral spirits enough to allow it to separate?

Michael
 
Since you are waiting for the mold max to arrive, and assuming you already made your master out of wood..spray the master with polyurethane to seal the wood pores. That will help tremendously because now your wood is plasticized. still helps to put a release on it as well, but it will be much easier to work with finished wood than unfinished.
 
Yep, seal the wood and then use your release agent mixture....you shouldn't have any problems.

I use vegetable oil wiped onto the sealed wood and it works also.

Let us know how it works out.
 
Thanks Charlie and Fred for the confirmation. I'll be interested to see how long it takes to get the mold max since it took 3 days and 2 emails before I got the info on how much shipping would be:eek:

Michael
 
Shouldn't take long..I usually get it in a day or two. Make sure you mix it really really really good. I took an old spade drill bit and ground off the point and chuck it in my drill as a mixer that fits into a cup no problem, and cleans up real easy. Expect it to take 24hrs before you can remove it from master and it will be several days later before it completely cures...not that you cant use it in the meantime.
 
I confirmed the order Friday morning. It just depends on when they decided to ship. As I said it took this company 3 and a bit days just to give me the cost of shipping.

I like the idea of the ground off spade bit. I have an old beater from a mixer that I have used in the past for different mixing but I know that I have an old bit that I can sacrifice.

My friend delivered my Alumilite today so I will soon be set to try things out but I still need mt lathe drive to come back.

Michael
 
Well it was an interesting experience making my first mold with Mold Max. I think my shop was a bit cool so that probably caused the silicone to be thicker than it should be for mixing. I used a paint stirrer in my cordless drill and seemed to get it mixed well. Since I needed the full 2 lb kit I just poured the catalyst into the pail of silicone. I think I would have been better to put it in a larger pail right from the start. After mixing, and mixing I poured it into a larger pail and mixed it some more before putting it under vacuum. I did the recommended 3 minutes and decided it still looked like it had lots of air so did an additional three minutes. Then I slowly poured it into the mold and scraped out as much as I could from the pail. After it had cured for about 18 hours I started to demold it. Before pouring the mold had been sealed and then treated with three coats of petroleum jelly & mineral spirits mix, allowing each coat to dry before applying the next. All parts of the mold received the same 3 coats. When I started to demold it 2 of the sides didn't want to release. The other 2 sides separated relatively easily and the base came off really easily. The four dowels that were used to create the cavities for the stopper blanks even came out pretty easily although I did have to gently apply compressed air down the side of one. I had to kind of slice the stubborn 2 sides off. Good thing this mold will be used by me because cosmetically on those 2 sides it ain't pretty.

If I am going to make a second stopper mold I think I will recut the sides out of the same material as the base since it separated so easily.

I know - no photos it didn't happen but right now it is in a toaster oven post curing as per Smooth-on's instructions.

Photos might follow tomorrow and hopefully some stopper blanks in a couple of days.

Michael
 
Congrats on yet another new addiction! :tongue:

I wouldn't worry about the 3 coats of release, as the mixture contains a
solvent, so you will (in effect) just be removing and replacing the first coat.

Not sure why two sides wouldn't release.. unless somehow you got the
silicone into the wood. I suppose that could happen if the coating hadn't
completely cured.. the mineral spirits might have started to soften it, or
the alcohols in the silicone may have seeped into it and drawn in the rubber.
(depends on what you used for a finish on the wood) Also, if there were any
cracks in the wood or a really rough texture, the rubber could hold onto that. Waxing the wood may also help.

If the silicone is too thick for your taste, you can thin it with up to 10%
silicone oil. That makes it easier to work, but keep in mind it affects the
hardness and the dimensional stability. For bottle stoppers, that may not
matter at all. Also, when you add catalyst, make sure you include the
thinner in your equation. If you use 100 parts silicone, use 10 parts catalyst.
But if you add 10% thinner, now you need 11 parts catalyst.

Look forward to seeing the mold and blanks!
 
Wow lost a ton of typing because I hit a wrong key. Sides were all a vinyl or something similar covered particle board so I don't really understand why 2 released and the other 2 didn't. Base was a veneer covered chipboard core that already had a finish. The only unfinished pieces were the dowel and they were sealed with 3 coats of water-based poly. They still soaked up the mold release and that was the reason for all the coats of petroleum jelly/mineral spirits release.

I actually wonder whether I made the walls too thick and could have gotten away with thinner walls and therefore less silicone. I'm looking forward to doing the first casting in the mold because I have never worked with Alumilite before. I'm also hoping that after all the expense involved that the potential order comes through. Haven't heard from them in a few days:eek:!

I've learned a lot through this process and appreciate all those that offered suggestions. Newlondon88 (Charlie) and PTownSubbie (Fred) have been a lot of help as have others.

In the next few days I'll get some photos posted for sure. I just have to get things set up because I have a lot of photos to take and then post.

Michael
 
I remember my first mold. I made the master from corian. The entire thing was glued together, so removing the silicone was impossible. It's not that the silicone couldn't be pulled from the corian, but there was no way to get to my hands to the bottom to pull it up and out. I ended up using a chisel and hammer and breaking the master to get it out..and the mold worked great. Now my hand made masters are all screwed together so I can unscrew the sides. It's a learning curve.
 
yup everything was screwed together. Got the screws out and then removed the 2 short sides pretty easily. The base just peeled away no sweat. Pulled the first 2 rowels out just using my fingers and got the third one using one of the bolts that I used to hold them in place originally. The last dowel needed the blast of air down the side but that was pretty slick. Used a hack saw blade to separate the 2 stubborn sides.

As Charlie said, it is a new addiction and I have one 2 lb kit left right now. Just contemplating whether or not I need a second stopper mold or whether it it will go to something different.

Thanks Jeff for all your input in this and my casting questions.

Michael
 
Okay, this is an interesting thread. It all seems like a lot of work. I am not a "caster" yet. I have only cast a couple things so far (a soft piece of wood to turn a box out of and a pinecone to make a bird house out of), not a blank to make something out of. I am getting set up to try my hand at casting, have most the needed stuff, but I was planning on using something like a pill bottle for a mold for bottle stoppers and then just turn the bottle off when I put it on the lathe. Would this work? What is the advantage of making a mold?
 
I'll bet the two sides that stuck had some endgrain showing and the others didn't. Endgrain or open grain should be fully sealed with some type of laquer so that the mold material cannot penetrate.

Since I started using UHMW sheets, I have no problems removing my sides from my molds. I still use wood but it is fully sealed with laquer so that they are sealed and smooth. Makes a big difference!
 
Pill bottles will work. Many people on here recommend them for stoppers. I just didn't want to have to have a supply of bottles and get rid of the scraps after turning them away. Lots of others told me that the blank should slip right out of the bottle no problem except it never worked that way for me so I decided that a mold was the way I wanted to go. It is reusable, I set up some markings for various kinds of pours and it was neat to try working with the material. Really neat how once it is cured the leftovers just peel out of the mixing pails for cleanup.

No endgrain on the boards that stuck. They are coated with some kind of white plastic-like film but so were the 2 sides that released without a problem. We have a local surplus store that sells UHMW so I may just have to check that out.

Michael
 
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PaulDoug said:
but I was planning on using something like a pill bottle for a mold for bottle stoppers and then just turn the bottle off when I put it on the lathe. Would this work? What is the advantage of making a mold?
Click to expand...

Yep.. it would work.
The advantage to using a mold is that you don't have to swallow as many pills.

The pill bottles are one shot. If you have access to lots of them, then go
for it. But a lot of people don't, and they can get pricey when you go to
buy them. Plus, you can store one mold .. or bags of pill bottles..
 
Good points on the pill bottles, except when you get my age you seem to accumulate a lot of them. The was a time I didn't have many around.

If you get a chance I hope you will post a picture or two of the molds you made.
 
Finished mold

Here is the photo of my first silicone mold. Haven't had time to cast yet but hopefully in the next day or two. I tried to show the registration lines I incorporated into the mold as well as the nub that will make the centre hole for drilling.

Michael
 

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Charlie - you're making me blush!

Jeff - I can't wait to try it out. Now if someone would just set me straight on what I have to do to get swirl patterns with 2 different colours I'd be off to the races.Well maybe I might wait until the daylight hours.

Michael
 
Doesn't matter what kind of resin you use, PR or Alumilite, swirl colors are created by mixing colors together. You want black and white swirls, then you mix up one cup black and one cup white. Then you pour the two into the mold. The key to success is gel time of course..that's where it gets tricky. with alumilite your timing is less critical as the product gels much faster. with PR you need to wait for the cups to start heating up before you pour. If you don't wait, the colors will seperate out and you'll have the heavier color settle to the bottom. It's all about learning the timing. This way the resin sets while the swirled colors are suspended in animation.
 
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I just use PVC pipe cut to 2" lengths for bottle stoppers. Painters tape on the end, no release agent needed. When cured, usually 3/4 hours (PR) peal the tape and they push right out.
 
I tried that Scott and it didn't work for me. Worked the first time and then I had to pound the last ones out and they were all fractured. I checked to make sure I was using the right type of pipe. I got frustrated with trying to figure out why others could make he PVC or pill bottles work and I couldn't. That's why I decided to try the molds and figured I might as well have the fun of pouring my own.

I think today is the day to make the first cast so stand by for an update.

Michael
 
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