Make a mold from a resin part

lukebrynycz

lukebrynycz

Sr Member
I have a part that is already resin from a previous mold. I'm wanting to make another mold from this part, but I'm new to this. I've figured out most of the process, but I'm confused with one bit... Do I need to seal the part, and THEN cover it with release agent (I was going to use Mann ease release 200).

I couldn't see anywhere that any of the sealers OR release agent worked with resin.

Also, I'm guessing if there are screw holes, I need to fill them with something like chavant nsp clay?
 
Without seeing the piece your moulding, a resin casting shouldn't require sealing as it it's a non porous material and I personally wouldn't bother with release agent as I find it unnecessary - and I don't like having to clean it of afterwards.
Any deep holes can be filled with clay or plasticine.
 
Pro Mod said:
Without seeing the piece your moulding, a resin casting shouldn't require sealing as it it's a non porous material and I personally wouldn't bother with release agent as I find it unnecessary - and I don't like having to clean it of afterwards.
Any deep holes can be filled with clay or plasticine.
Click to expand...

It's a piece of clear resin that has been painted with rustoleum primer. I was only going to use a release agent to ensure that it didn't pull off this paint from the part, or does it not pull paint off? I'm using Mold Max 30 by the way!
 
It shouldn't pull the paint of, but it depends how well the primer has bonded to the resin. If the surface was sanded prior to application it should be fine, however you may as well use the mould release as you have it - better to be safe than sorry!
 
Pro Mod said:
It shouldn't pull the paint of, but it depends how well the primer has bonded to the resin. If the surface was sanded prior to application it should be fine, however you may as well use the mould release as you have it - better to be safe than sorry!
Click to expand...

Cheers mate! I'm not actually bothered about the paint anyway, as long as the mold didn't damage the resin part at all, then I'm happy. I've got sprare primer to give it a once over anyway, and I think I'd rather do that than have to prat around cleaning release agent off them.

Does release agent help prevent bubbles though?
 
Depends what mold material your using. If its a silicone mold the part will come right out. The only thing
youll have to do is make sure you mold release the other mold plug surface which usually means
spraying one side of the part. I can never get hold of mold release so I just use hairspray.
works the same. A couple of layers does fine with me. I always try and clean the excess
hairspray off the part though cos sometimes when I make the part from the mold one side ccomes out
a bit shiny. Doesn't matter as you can sand it anyway.
 
Mold release is mostly used for the casting process to extend the life of the mold rubber. I seldom use it for making the mold unless it's something strange.

Silicone doesn't stick to anything (almost). That's why its such a good molding material. About the only thing that silicone does stick to is silicone. So if you are doing a clay-up 2 part mold, then you will want to spray the first half with release before you pour the second half so they don't become one solid block.
 
Mould release does not help prevent bubbles.
Mould design, careful mixing and pouring of rubber and resin are the best ways to reduce possible defects.
Let us know how you get on.
 
Mold max 30 is a tin based cure silicone if I remember. Good choice. You will still most definitely need to use
A mold release sprayed/thinly brushed onto the surface of the mold with te part in it. Remember to cut some
'Keys' into the first part of the mold so both parts of the mold will line up correctly.
So definitely to answer your question your part will come out quite eeasily from the silicone mold without pulling tthe paint off.
done heaps of molds and had no problems using painted parts. Just make sure you definitely mold release the frst part of the mold or the second layer of mold will stick to you first. Another thing I do is I brush the silicone on the
part while it is in the mold. If I'm not doing intricate parts I don't bother vacuum the mold in a chamber. That gets all
if not most air bubbles out.
 
edspaged2 said:
Mold max 30 is a tin based cure silicone if I remember. Good choice. You will still most definitely need to use
A mold release sprayed/thinly brushed onto the surface of the mold with te part in it. Remember to cut some
'Keys' into the first part of the mold so both parts of the mold will line up correctly.
So definitely to answer your question your part will come out quite eeasily from the silicone mold without pulling tthe paint off.
done heaps of molds and had no problems using painted parts. Just make sure you definitely mold release the frst part of the mold or the second layer of mold will stick to you first. Another thing I do is I brush the silicone on the
part while it is in the mold. If I'm not doing intricate parts I don't bother vacuum the mold in a chamber. That gets all
if not most air bubbles out.
Click to expand...

Thanks for the tips! I'm actually doing a one part mold as one side is completely flat and it looks a lot easier.

So basically:

When making the mold FROM the original piece, I don't need a release agent. But when actually making my first resin pieces from the mold, I need to use a release agent?
 
Oooooohhhh. If your only doing a one part mold then it'll be **** easy mate. Make sure you have a flat surface and check it with a spirit level. If it looks level enough then should be alright. If I'm making a flat part mold I dam off an area using plasticine. Non sulphur based plasticine. Basically just modelling plasticine like that old kids TV show green character 'Gumby' was made from lol. Get that flat part you want to mold and make a thin sausage of plasticine and place it around the edges of said flat part. This stops the silicone from getting in underneath the part. Push the part down so the plasticine pushes out the sides. Clean the excess off. You can now pour your silicone into the dammed off area. Like I said before I brush the silicone into all the nooks and crannies of the part so there's no bubbles. Silicone won't stick to the plasticine either.

You could also roll a piece of plasticine into a flat round pizza base shape and do the same thing. Dam the area off around the part. Push the part in slightly into the 'plasticine pizza base'.

Lastly: no you don't need a mold release. If it's a flat part and your using a silicone mold you won't need a release agent. The resin once it's dry won't stick to silicone.
 
edspaged2 said:
Oooooohhhh. If your only doing a one part mold then it'll be **** easy mate. Make sure you have a flat surface and check it with a spirit level. If it looks level enough then should be alright. If I'm making a flat part mold I dam off an area using plasticine. Non sulphur based plasticine. Basically just modelling plasticine like that old kids TV show green character 'Gumby' was made from lol. Get that flat part you want to mold and make a thin sausage of plasticine and place it around the edges of said flat part. This stops the silicone from getting in underneath the part. Push the part down so the plasticine pushes out the sides. Clean the excess off. You can now pour your silicone into the dammed off area. Like I said before I brush the silicone into all the nooks and crannies of the part so there's no bubbles. Silicone won't stick to the plasticine either.

You could also roll a piece of plasticine into a flat round pizza base shape and do the same thing. Dam the area off around the part. Push the part in slightly into the 'plasticine pizza base'.

Lastly: no you don't need a mold release. If it's a flat part and your using a silicone mold you won't need a release agent. The resin once it's dry won't stick to silicone.
Click to expand...

Great idea on the clay under the flat surface. I was wondering about that actually as it's not perfectly flat on the edges, but has slightly rounded edges. I don't mind it being straight and then doing a tiny bit of sanding on the corners afterwards!

So when I'm pouring the mold into the enclosure, once it starts to flow over the top of the resin part, use a brush in the little holes and cutout sections? I've seen a tutorial where someone used latex gloves and used their fingers gently once all the mold max had been poured in?

Regarding the mold release, it's flat on the bottom but has a few jagged edges on top with a small small cutout sections. Still don't need mold release?
 
Yeah you could use a glove but the brush really gets it in there. The brush tends to be a write-off afterwards. As for the small cut outs on the part you should be fine. Silicone is very flexible and the part will pop right out mate.

Could you post a pic of the part?
 
edspaged2 said:
Yeah you could use a glove but the brush really gets it in there. The brush tends to be a write-off afterwards. As for the small cut outs on the part you should be fine. Silicone is very flexible and the part will pop right out mate.

Could you post a pic of the part?
Click to expand...

Sure! I have a crack on a flux box and just wanted to create myself another one. Here's a pic that's already hosted on therpf:

http://i31.photobucket.com/albums/c387/staermose/Flux-box.jpg

Also, one from one of Garys builds: http://i.ytimg.com/vi/WfQvhYSKnqc/0.jpg

As you can see, there are a few little cutouts. I plan on filling all the bolt holes with some chavant NSP to make sure it's a smooth finish and can redrill the holes to the exact size rather than guessing with the mold.

I would have thought that dipping a glove into the mold whilst in liquid form would create little air bubbles rather than remove, or do you simply dip the brush into it and brush into the corners and cutouts, THEN start pouring into the corner of your enclosure around the part? Thanks for your help so far, as you can tell...I'm new to this ;-)
 
Nah mate what I do is when the part is all prepped In the plasticine I then mix the silicone with the catalyst. The stuff I use is 2-5%. I then start dabbing the part getting into all the nooks and crannies. That just makes sure all the air bubbles are out or there's less of them. Less cleaning up to do on the finished resin part. After that, I then pour the silicone at a height so it's a small stream. I'll just keep pouring it in slowly so you can see the silicone rising above the part.

Are you building a flux capacitor? I'm planning on buying a delorean as a project lol
 
edspaged2 said:
Nah mate what I do is when the part is all prepped In the plasticine I then mix the silicone with the catalyst. The stuff I use is 2-5%. I then start dabbing the part getting into all the nooks and crannies. That just makes sure all the air bubbles are out or there's less of them. Less cleaning up to do on the finished resin part. After that, I then pour the silicone at a height so it's a small stream. I'll just keep pouring it in slowly so you can see the silicone rising above the part.

Are you building a flux capacitor? I'm planning on buying a delorean as a project lol
Click to expand...

lol! It's hard to understand stuff online without seeing pictures, but I assume you mean dab the mold max 30 over the resin part as a bit of an initial coat, THEN pour it around the part and let it flow over?

Already got a Flux from Bruce ;-)
 
That's exactly it. That's how I do it and never fails me ;) when I get back home in a week ill post a pic of a flat mold. Always good to have spare molds cos I always end up mixing too much resin so its good to have random molds to pour into.
 
Another quick question please! :)

If I have a prop that has a flat surface (just need a one part mold) but it's not 100% flat to the bottom of the container, what will happen if I don't secure it down with modelling clay? Will it just seep under a little around the edges? I know it won't look amazing when the mold is done, but I would imagine that as long as you can pour in the resin afterwards, you could just pour slightly short of the top so the resin part comes out flat? Does that make sense..?
 
I like to do one sided moulds when ever I can... just makes life so much easier. First I use lego blocks to build a wall and then I use packing tape to seal up the bottom, then I put the flat side of the piece that I want to make a mould of on the sticky side of a wide packing tape. turn it upside down and use a fingernail to make sure the tape is fastened around the edges, if It it is not entirely flat, but the tape is good on all edges, you should be good to go. Personally, even if a bit of silicone gets in there, you can either trim it back later or leave a slight ridge, you will have a bit access that you will have to sand away, but then you are sure that you have enough resin and it does not matter so much if the mould is perfecly flat when casting.
 
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