The Magic Café
Username:
Password:
[ Lost Password ]
  [ Forgot Username ]
The Magic Cafe Forum Index » » I'm a real boy! » » Working with fiberglass (0 Likes) Printer Friendly Version

rcav8r
View Profile
New user
8 Posts

Profile of rcav8r
I've been rereading "Figure making can be fun?", and have a couple of questions.

First, why not make a fiberglass mold directly over the clay model? in other words, skip the rubber.

And is there a reason one can't use silicone spray directly on the clay for a mold release?
damien666
View Profile
Special user
canada
513 Posts

Profile of damien666
I have not read the book you are referring to but I have extensive experience with all sorts of mold making techniques, so I will try to answer your question.
You can certainly make a fiberglass mold directly on a clay sculpt.. The thing you have to keep in mind is what the final piece will be cast out of. If you are going to make the end puppet out of a flexible material, you will have no problems pulling that out of a rigid fiberglass mold. If, however, you will making the puppet out of a rigid material, you will most likely want a flexible mold.. Otherwise, if your sculpture has undercuts, your rigid puppet 'skin' will get permanently locked into the mold..
There is a good rule to follow: for a rigid casting, use a flexible mold; for a flexible casting, use a rigid mold!
Good luck with your puppet making!
Damien
http://www.puppetsandgore.com
maps
View Profile
Inner circle
1122 Posts

Profile of maps
Damien knows what he is talking about! He just made me r/c old man puppet and it's a work of art that works very well.
the heart is where the magic begins
Visit my website
[www.mascotsandpuppets.com]
TheDummyDoctor
View Profile
New user
U S A
76 Posts

Profile of TheDummyDoctor
Damien's got it exactly right. I don't work with fibreglass too much any more since for the last 7 or 8 years I've largely gome back to wood based materials and only doing custom one-of-a-kind figures. Butif you're bent on making a head from fibreglass (or urethane or other resins) a silicone mould is definitely what you want to make your headshell castings from...otherwise you might have trouble extracting the headshell from a rigid mould (unless you have gone through the trouble of making a carefully shimmed, multi piece mould).

Now, on the other hand, if you were referring to making the actual headshell from fibreglass right over the clay scupt, you would have no problem removing that from the clay. The problem will be in all the sculpted detail you will have lost by doing so. If you are working in fibreglass or other resins for the head, negative mould (preferably flexible, such as silicone) in the only effective way to go.
-------

Alan Semok, Ph.D (honoris causa)

THE DUMMY DOCTOR

Building Pro Vent Figures since 1966

web: www.AlanSemok.com/dummies
rcav8r
View Profile
New user
8 Posts

Profile of rcav8r
A multipiece mold that would allow for the undercuts is what I'm talking about. I do have some experience making fiberglass molds and parts for radio control airplanes, so that's where I'm coming from, making molds directly on the parts.
I'm just otherwise wondering if there was some other reason why not to make a mold over clay, and if the author of the book left out any mention of using silicon spray for a reason, such as either he wasn't aware of it, or it reacts with the oil base clays, or if it wouldn't be enough. He recommends using vaseline rubbed over the model before putting on the latex rubber.

There are also the paste wax releases, but given that a little force is needed to "melt" these, it'd probably deform the clay.
TheDummyDoctor
View Profile
New user
U S A
76 Posts

Profile of TheDummyDoctor
If you've got the knowhow to make multi-piece moulds, then sure...you can do it right on the clay with resin & glass. You'll want to watch the undercuts particularly carefully since you want to be able to remove the hard casting that you'll ultimately be making from the hard mould. In my experience, there's no reason why you cant use silicone on the clay as a mould release, and you'll certainly need to do that when you make your casting from your fibreglass mould. If you intend to re-use the clay afterwards, it may affect the texture / consistency of the clay to some degree.

If you do the mould using silicone (and assuming you're using the right type of clay) you don't really need to use a mould release at all (on the clay OR when you make the casting from the mould).
-------

Alan Semok, Ph.D (honoris causa)

THE DUMMY DOCTOR

Building Pro Vent Figures since 1966

web: www.AlanSemok.com/dummies
damien666
View Profile
Special user
canada
513 Posts

Profile of damien666
Howdy..
Thought I would chime in about A couple more things..
if you are doing a fiberglass mold directly onto clay, I would recommend using a clear coat as your sealer.. I use kryolan crystal clear.. Just let it dry before starting to mold.
It doesn't gum up the clay and it works on oil AND water based clays..
PvA is a common release when running fiberglass next to fiberglass.
There is always going to be some clean up and scrubbing of a mold regardless of the release you use.
Also, as a side note from something you mentioned above.. I would recommend not using Vaseline with latex... It degrades it.
Oh yeah - if you are doing a Fiberglass mold right onto the clay, you will want a gel coat to pick up the detail before backing that up with matting or cloth.
Also.. On a cautious note - PLEASE use a proper respirator when working with mekp, cabosil, glass cloth and polyester resins.. It is toxic stuff and the particulates will kill you!
I used fiberglass resin so much in special effects work that I developed a strong sensitivity to it.. I can't use it anymore at all.. So please be careful! Read your msds sheet!
Damien
The Magic Cafe Forum Index » » I'm a real boy! » » Working with fiberglass (0 Likes)
[ Top of Page ]
All content & postings Copyright © 2001-2021 Steve Brooks. All Rights Reserved.
This page was created in 0.09 seconds requiring 5 database queries.
The views and comments expressed on The Magic Café
are not necessarily those of The Magic Café, Steve Brooks, or Steve Brooks Magic.
> Privacy Statement <

ROTFL Billions and billions served! ROTFL