Help I am stuck !! Decorative Concrete Mold Release Agents
Ok, I am not really stuck, but I thought I would pass on some information on release agents for your decorative concrete latex and fiberglass molds.
I have been in the concrete business for quite a few years and I have made latex molds and pour concrete ornaments using latex molds. Latex does not like petroleum based products as well as sunlight. Your best bet is a castor oil mixed with methyl hydrate or isopropyl alcohol (1 part castor oil and 8 parts methyl hydrate). Add the mix to a spray bottle and shake it well before each use. Just a light spray with the mixture, remember that too much is bad as it will stop the concrete from setting.
A secondary option that I hear quite often is Pam or vegetable oil. These are ok and will w0rk, but not as good. These will also get sticky and hard on your rubber unless you wash it off after each use.
A third option is a pre-packaged aerosol spray can such as Crete-Lease or Synlube 531 as examples. These work extremely well, but can be expensive in comparison.
As a warning for latex rubber molds any kind of petroleum based oil, such as (motor or mineral) is bad as it will turn your latex into soft liquid mush!
I did come across this nice headless man giving a good demo on mixing and applying the castor oil mixture: Youtube video on applying release agents. He must not like the camera much…
As for fibreglass molds, you can use almost any kind of oil as long as it does not stain your concrete. If the concrete absorbs it, there could be a layer on the outside of your finished concrete which won’t let you apply any finish to the sculpture. I find it just easier to apply the same castor oil mixture.
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Using Decorative Cement Mold Hints 
on December 28, 2009 on 11:34 am
I bought some old Aluimum and cast iron molds this year at a flee market whats the best releasing agent to use , my father told me in the 1930 ‘s on cast iron ones they used candle wax .
I also heard old motor oil .
I’m also wondering if I should repaint the inside of the molds ?
Bob P
on January 5, 2010 on 1:42 am
Thanks to provide such a good article, to learn it!
on January 5, 2010 on 3:31 am
Hi Bob
You can use almost anything with them but you want to make sure it does not stain you concrete so you can finish them. Car wax and and motor oil will work, but if they attach to the concrete you will not be able to paint or stain the concrete afterword. Try using vegetable oil thinned down with some alcohol as it is cheap and will just absorb into the concrete.
Have fun!
Tim
on March 7, 2012 on 4:45 pm
Thanks! Bought an old iron mold at an auction and this helped tremendously in what to use for ‘releasing’.
on May 1, 2010 on 11:12 am
Hi
I always use washing up liquid for removing the mould. I put a small amount of washing up liquid on to the latex smother it all over and wait a couple of minutes and it peels off easily.
on May 2, 2010 on 3:58 am
Hi James
Be careful with the different washing liquids as some contain petroleum product and can break down your latex rubber over time.
Tim
on May 2, 2010 on 11:17 am
Hi Tim
Thanks for the advice, that is a worry.I usually use a watery washing up liquid not a strong liquid.What would you recommend for a mould release ? .I have looked at your blog regarding mould release and i dont know where i can buy methyl hydrate in the UK.I dont want to damage my latex moulds.
on August 5, 2010 on 11:49 pm
HI,
I want to make some moulds what do i put on the item i want to make a mould of so the latex does not stick to it.
on August 7, 2010 on 2:23 am
It depends on what your master is made up so you do not ruin it. It might be best to check with the company that made the latex rubber to see what works with their rubber. I use a simple wd-40 silicon oil.
on November 9, 2010 on 8:59 pm
Having some problems releasing concrete from their fibreglass moulds…I’m told the inner should be released first however the suction is strong & even a winch is not woring. Have resorted to unbolting the outer first to remove the seepage around rim of the pot before trying to pull concrete pot from the inner. Is it best to release inner while concrete is still wet or wait till dry dry (maybe a few days)…what do you think? Currently using a concrete release oil supplied by the concrete outlet.
on November 11, 2010 on 10:58 am
If the inner is sticking you will need to add an air hole to it to release the suction. Wait the 24 to 36 hours before you demould the concrete.
on April 9, 2012 on 11:23 pm
Cathy iam having the same problem. What did you do?
on January 3, 2011 on 1:34 am
[…] Help I am stuck !! Decorative Concrete Mold Release Agents July 2009 10 comments 3 […]
on April 17, 2011 on 10:06 pm
Hi Bob
I want to make a concrete bowl using a metal wok as my mould. My husband has offered me some silicone grease to use as a release agent, Would this be a good option or should I stick with the vegetable oil and alcohol as you suggested previously.
Thank you
on April 17, 2011 on 10:18 pm
Hi Sarah
You can use silicone grease, it may make you concrete waterproof as the silicone will get in the concrete. How are you going to make the inside of the bowl? You will need a corresponding bowl size to sit in the middle.
Tim
on August 22, 2011 on 8:17 pm
Tim i have a wooden mold sealed with gloss paint for making concrete pillar tops and was wondering if beeswax or floor polish wax would be ok for a mold release agent, would i need to put a couple of coats on
on September 17, 2011 on 1:50 pm
Yes that will work.The wax could seal the concrete so that you can not paint it though.
on September 17, 2011 on 1:52 pm
WIth the water leaking it causes the concrete to be weak. You must find a way to seal the water in.
on October 18, 2011 on 1:53 am
Hi Tim –
Have just been the recipient of a number of ‘Mayco’ molds that I would like to use concrete with. I understand that these are usually used with clay.
Are they usable and if so – what kind of release?
on October 18, 2011 on 3:53 am
HI Aims
The reale agent really depneds on what the mold is made of. With latex rubber you can not use petroleum based oils. You could always try vegetable oil.
TIm
on October 18, 2011 on 5:26 am
Sorry Tim – forgot to ask what the molds were made of – apparently they are made of plaster of paris.
Any clues on this?
Thanks!
on October 18, 2011 on 6:28 am
HI Aims
I think you will need to use wax to seal the molds so water does not leave the cement otherwise they will not work.
TIm
on October 18, 2011 on 5:38 pm
Any special kind of wax Tim? And does this become my mold release as well?
on October 19, 2011 on 4:07 am
just some cheap rub on car wax maybe.
on December 9, 2011 on 12:18 pm
i want to prepare cheap concrete mold release oil kindly help
on December 11, 2011 on 12:19 am
It depends on the type of mold will dictate the type of release agent. You can use 1 part castor oil and 3 parts denatured alchohol.
on February 13, 2012 on 2:21 am
We are buying rubber molds and we just got some large lions and and owls but we did not get a backups what would work for a back mold the best way that would work
on September 16, 2012 on 10:59 pm
hi fibreglass resin is sticking to my latex could you tell me what release agent i need please
on January 20, 2013 on 1:05 pm
Are you using resin inside the rubber? If the fibreglass is your casing then wax your fibreglass.