latex glove mold question... plaster mold alternative?

I'm going to attempt to make new latex cyberman gloves. My last attempt didn't go well with the plaster.
I understand that plaster molds are the way to go. But they also quickly fail, like you may only get a few pulls from them (and I'll likely have friends that want them if it comes out half-way decent). And in making the mold, you typically destroy the clay sculpt getting it out of the plaster.

Can you use something more permanent like resin or plastic as your negative instead of plaster? Or is there some other method that is preferable?

Thanks for looking!

Hi,
i used to do plaster molds as most molders begin with plaster. Are you using the correct plaster and not the craft plaster? You can add layers of hemp to give it strength. Typically unless they are thin or dropped they last a while. Plaster is the best material when casting in latex because it is pours. Some people say you can't cast latex with silicone. Which I have done, but it is a pain in the ass. The latex must be done in many many thin layers. The same for fiberglass.
I would assume that with most molding processes there is some damage or complete damage to the sculpture.
Fiberglass was the next molding techniques i learned. It's nice and light weight and can really take a beating. It's cheap but it's also very harsh to use and requires a lot more clean up as there will be many sharp shards waiting to cut you. But there is also fiberglass cloth and chopped fiberglass. Experiment experiment experiment!
Good luck

I've used a couple types of plaster, Can't seem to get it into all the cracks and crevices that I need. Or if I do, they don't bond to the larger mold or snap off easily. Could just be the fiddly bits are too detailed? IDK

I was thinking about something like this which I stumbled on last night (someone posted it on the rpf but I now can't find that thread:

Silicone Prosthetic Mold

"Can't seem to get it into all the cracks and crevices that I need."
Plaster has to be liquid enough to capture all the detail. Also the way you lay it on the sculpt is important. If the palster is liquid enough (the correct ratio mix) blowing over it to force it in is a way. You can also use a chip brush.
Besides blowing, some people literaly "spalsh" the first coat against the sculpt. This forces the material into the cranies etc.. then blow to ensure there will be no bubbles.
The splashing method can be sloppy without experience, the chip brush and blowing will be cleaner.

How are you applying your first plaster splash coat (copy coat)?

"Or if I do, they don't bond to the larger mold or snap off easily."

Are you leaving the splash coat too long before moving ahead..I mean for many hours or a day?. This could cause delamination.
Adding fresh plaster over very dry plaster can produce this.
If you have to, damp the previous layer with water and go ahead with the rest of the mold. Better to make the piece in a row.

What plaster are you using?. Some times if the details are too weak stone plaster is a must.

As for the video, you don´t need that techniche to cast latrex gloves. The dweling system is the way to go, you don´t need a core. Fill it to the top, let dwell for three hours aprox, empty and let dry. Yoll get a good and even thicness this way. Besides they are using a PU resin. Not good to cast latex at all. And the molding technique is a particular one for prosthetics, prepared to allow the excess of material to come out.

udog said:

Plaster has to be liquid enough to capture all the detail. Also the way you lay it on the sculpt is important. If the plaster is liquid enough (the correct ratio mix) blowing over it to force it in is a way. You can also use a chip brush.
Besides blowing, some people literally "splash" the first coat against the sculpt. This forces the material into the crannies etc.. then blow to ensure there will be no bubbles.
The splashing method can be sloppy without experience, the chip brush and blowing will be cleaner.

Click to expand...

It was very liquid. Not sure how to describe it. Much closer to milk than milk shake? Not sure what you mean by blowing it... like with a compressor?

udog said:

How are you applying your first plaster splash coat (copy coat)?

Are you leaving the splash coat too long before moving ahead..I mean for many hours or a day?. This could cause delamination.
Adding fresh plaster over very dry plaster can produce this.
If you have to, damp the previous layer with water and go ahead with the rest of the mold. Better to make the piece in a row.

Click to expand...

I've tried just a splash coat, probably my technique but I missed a lot of detail. The second time I doing like a slow splash coat plus using a chip brush to force it into the crevices and then continuing with the splash coat.That got more detail, but I think the problem was it didn't build enough rigidity to be able to retain the detail, the negatives easily came off (not scrubbing/picking hard at the clay, just enough and whole sections came out). The longest I tried opening the mold was 6 hours, the first was 2, the second 4. I know what you mean by delamination. I left a small trial over night using the 2 pour per half technique and after I got it separated it came apart in pieces.

I laid the glove sculpt horizontally like the one laying on the table and had it supported in the box I made with foam board. I then did two pours per half, very quickly following each other. Letting the one half set for about 30-40 minutes, spraying between them with mold release (though I've also tried using Vaseline). The gloves are finicky, image below.



Edit, I should also say that on the next glove, I intend to not go as deep with the detail lines. They were about 1/8". I think I can get away with less and use paint to get a deeper effect. The palm of the glove was before I found a good reference photo, so I channeled Iron Man a bit

udog said:

What plaster are you using?. Some times if the details are too weak stone plaster is a must.

Click to expand...

Started with a giant bad of plaster I got at the local pottery supply place. Didn't work well, but I've tried both ultracal and hydrocal as well.

udog said:

As for the video, you don´t need that techniche to cast latrex gloves. The dweling system is the way to go, you don´t need a core. Fill it to the top, let dwell for three hours aprox, empty and let dry. Yoll get a good and even thicness this way. Besides they are using a PU resin. Not good to cast latex at all. And the molding technique is a particular one for prosthetics, prepared to allow the excess of material to come out.

Click to expand...

I wasn't going to use their whole system, but it intrigued me to use resin instead as I think I can control the mixture easier. Plus I'm currently in an apartment with no easy outside area to work. Plaster is a giant mess... or it is when I use it anyway. lol

Is there another resin that would work better for this? Thanks so much for the input. Very much in learning mode here.

Another thing I've done is switch to an oil based clay. I figured that since it is a much longer working time, you really don't have to worry about it drying as much, it would be easier to control moisture during the mold curing process. (Also my sculpt won't just up and crack if I need to leave it sit for a day due to work. Any truth to that hunch?

"Not sure what you mean by blowing it... like with a compressor?"

For something that size your lungs should do. The idea is pushing the material into the detail when it´s liquid. It can make a diference.

"Is there another resin that would work better for this? "

For casting latex, it´s not a good idea. You need a porous material.
Anyway, resins are toxic (Isocianate). So it´s not that good using it where you leave, and less where you sleep (just in case).

"Another thing I've done is switch to an oil based clay. I figured that since it is a much longer working time, you really don't have to worry about it drying as much, it would be easier to control moisture during the mold curing process. (Also my sculpt won't just up and crack if I need to leave it sit for a day due to work. Any truth to that hunch? "


Not a bad idea, specialy for a hand or pieces with thin parts (fingers) that will tend to dry out. You can get nice detail with the oil based clay,and if you don´t want to worry about drying and cracking, good idea.

"Plaster is a giant mess... or it is when I use it anyway. lol"

Hehe, well, it can be...

Regarding the fumes, I totally agree. I'm building a fume hood/box equipped with an extraction fan at one of my windows. I understand an epoxy resin mold is not a good idea for latex... what about silicone? Or is it the same story where porous is preferred? I figure gloves need to be durable, so silicone is preferred?


If resin is still a bad idea in that case, I'll still build the fume hood to use as a spray booth...


My question on the blowing the splash/copy coat... if it's really liquid, why/how does it matter if I blow it in there? Won't it just run out? I seem to be missing something in my understanding here. Am I basically using small amounts and painting it on and slowly building up layers until the detail work is set and then finishing the rest in a pour?

"what about silicone? Or is it the same story where porous is preferred? I figure gloves need to be durable, so silicone is preferred?!
Do you mean casting the gloves in silicone?. It can be done (platinum silicone) but it´s a more complex molding and casting process.
Idealy you will need to make a core piece, and inject the silicone in. You might also want to ad a nylon/mesh reinforcement,
Also a degassing chamber is a good thing for this.
Yes, with paltinum silicone the porosity is not necessary and resins or fiberglass are an option in this case. As long as they don´t inhibit the silicone....postcuring is necessary sometimes.

" if it's really liquid, why/how does it matter if I blow it in there? "

First, careful with mixing it too liquid.This is, adding too little plaster. This would result in a weak and slow setting one. When you stick your hand with a glove in the plaster, if it all runs down, then it´s too liquid. It should stay on the surface. If it runs out, I´d say somethings wrong with the mix ratio...litle palster in it.
Blowing is a good thing. If the plaster mix is ok, then it will push it into the details.

"
Am I basically using small amounts and painting it on and slowly building up layers until the detail work is set and then finishing the rest in a pour? "

There are many ways of making a mold. Sometimes if you can place the piece horizontal a pour will do without splash coat if you are making a box mold, but it won´t hurt. Vibrating the mold will hellp in this case,
Generaly one splash coat and the the build up or pour should do.
By layers is ok too. But do it all in a row, dont apply a layer, leave it for a day and then another layer...delamination or similar can happen.
Also, if you are using a brush or similar, careful with moving around too much the plaster again and again...like mixing again and again. Plaster doesn´t like this. Once it´s mixed you just pick the plaster with the brush, dont makle more mixing motion. It will result in a soft and "dead" plaster. Just pick and lay.

Good luck, and post you progress.

Thanks so much for your advice. Using silicone seems a bit more complicated than I thought it would be so I'll hold off on that for now. I will absolutely post on my progress.

I've got one hand about 95% done. Just have to do some final cleaning and smoothing. I'll give the casting a go this weekend. And hopefully NOT make a mess of my apartment.



Edit: I really hate how this board manages pictures when you click the zoom link.

looking good!

A note on mixing plaster: The best way, in my experience, is to have your water in a bowl then sift/sprinkle your plaster in. When the water gets saturated with plaster it will create cracks on the surface like a drying mud puddle. let this sit for a few minutes (1-3) as you clean your area a bit. Then mix gently with a paint stick taking care to not introduce air bubbles. It will have the consistency of a thick pancake mix. This always creates a strong proper mix of plaster. You can then use a chip brush or fingers and do a copy coat. Slowly goop it on after that paying attention to it's consistency until it is about 1/2" to an inch. Before it sets completely add wet reinforcing material like burlap and gently press it in. Let it cure (30-60 mins) before your final batch. This will help prevent delamination and also reinforce it for your final batch.

To get back to your original question after it has fully cured and dried, and cleaned, you can liberally paint the surface with a thinned shellac or polyurethane and let dry. A few thin coats is best. This will help reinforce the surface for multiple castings.

Depending on how you created your mold (2 part or single) you can create an archive and production mold. After your first latex cast, seam it and correct any imperfections if necessary, then place it back in the mold and add more latex to create a super thick cast, and let cure. From this cast create a one piece mold. Mix plaster as before in a plastic bucket that will fit the glove well and brush a copy coat on, to get the details, then wearing the glove submerge your hand in the bucket. Remove your hand gently, leaving the glove and let set. You can then coat the inside with polyurethane as before. Once done and cured you have a production mold. You can repeat this many times for greater production.

Hope that was helpful Great sculpt by the way

Bonus tip: add 1/2 a teaspoon of table salt to your water (1/2 tsp : 1 liter) and this will decrease setting time of plaster, BUT it will slightly weaken its strength.