Making your own vulcanizer. [Was: How to separate wax ]

Jewelry Discussion
1

What a coincidence. I had also just thought out a design to make my own
rubber vulcanizer. I like to tinker and my workplace has a lot of
oilfield instrument parts which we scrap when they are damaged or
overtaken by new technology.

I have salvaged two 15 in x 13 in x 1/4 in thick top grade
aluminium plates which will be the basis for the top and bottom
platens of the vulcanizer. These platens will be supported by four
corner screw posts and kept apart by strong compression springs. The screw
posts will allow the plates to be brought closer, say from 2.5 in to 2.0
ins to fit the mold frame.

To supply heat to the platens I have stripped two old clothes irons ($3
ea from GoodWill Stores) one for each platen and will tap screw holes into
the iron face so that I can mount them direct on each platen. When
stripped a clothes iron is essentially a horshoe shaped heating element
molded right onto the iron’s base. So there’s lots of mass to distribute
the heat evenly and the element has enough power to burn through old style
wood ironing boards (remember?). All modern irons have thermostatically
controlled switches.
I removed that from the iron’s base and intend to screw it direct
onto the platen. This will allow the thermostat switch to sense
the platen temperature direct therefore enable fine temperature
control for each platen.

This is a thought design and I haven’t quite gotten around to
building it yet so bear with me as to when I can report on the
results. I haven’t even bought any rubber sheets yet - the catalog
is in the mail.

Have to ask your advice here :-

  1. is there a particularly standard or ideal distance between the
    platens in commercial machines to fit commercial mold frames? Its
    only a matter of changing the spring length. I can make thosemold
    frames too but its best to conform to what’s available in the
    market.

  2. what is the breakdown temperature of the rubber used to make the
    molds? That is at what max. temp. will the heat damage the mold?
    This will be important as to the type of base metal I can cast. I
    do not intend to work with precious metals yet.

  3. I understand the raw rubber comes in sheets 3/16 inch thick. How
    many layers these can you stack to build up a mold, say for a figurine 6
    inches high? When cured will the rubber meld to form an uniform mass?

I know about RTV silicone molds and resin casting but would rather
work with rubber molds and intend to build or buy equipment only for this
technique.

Kelvin Mok (klmok@shaw.wave.ca)

Home: (403) 463-4099 | Home FAX: (403) 430-7120

2

OK Kelvin, I’m going to answer a few of your questions. At least
try. 1st.: I would think twice about using Aluminum, as it is
soft and isn’t that good of a heat conductor. 2nd. : I use only
Castaldo mold rubber, gold to be exact. It vulcanizes @ 307’f,
and the instructions say 7 min. per slice, I do 10, it has worked
for me, with no problems. Your vulcanizer needs to be as close to
the 307’f as possiable with no variations. You will also need
pressure kinda like a press. Look at the professional
vulcanizers in the catalogs and you will understand what I mean.
When you put pressure and heat together you vulcanize the raw
rubber into a semi-solid form, or "cooked ", rubber. Then you
need to learn the fine art of cutting the molds to eliminate the
parting lines. If you get Castaldo mold rubber you will get more
info, as well as other mold rubber I’m sure. I don’t work for or
get anything for using Castaldo, it’s just the rubber I use only
now. Hope this helps and Good luck!.. Matt the Catt @ C.I.A.

3

You’ll find everything you need to know and lots more at
CASTALDO’s web page at: http://www. castaldorubber.com .You can click
on the link below.

What’s this about making your own vulcanizer? Excuse me, but this
is a dumb idea. I’ll bet that using a few simple scrap parts from
your shop and the hardware store you could build your own car,
computer, airplane and toaster. But would it be any good and why
would you want to do such a thing?? At the very best you’d learn
a lot and have a very inadequate and, for what it’s worth, very
expensive machine.

Michael Knight

4

Lets not be so hasty to bad mouth somebody else’s idea.
Remember, you probably don’t know the skills & abilities of
everyone on the list. There can be many reasons for someone
wanting to make thier own tools. I have to say that some of the
’home made’ tools I’ve seen are alot better than the commercially
available stuff. Less expensive too!

Let’s keep this list polite & civil. We’ll all learn lots more
that way.

I’m reminded of a story. A student who was reminded to be polite
to others said, ‘Why be polite, politness is just pretty words &
hot air.’ Where upon the teacher said, ‘All that’s in the tires
on a car is air, but it sure makes the ride a lot smoother.’

Dave