Monday, March 31, 2008

Lost Wax Casting Process

Finally I've gotten all my photos together to do a photographic tutorial of lost wax casting.

tools and the beginning of a flower ring

All of my waxes are made individually. I really enjoy working with brown wax the most. I've used hard waxes for somethings when needed, but they aren't my favorites. I've also used some red and pink wax that a friend uses in dental wax work. I've made several of my own tools - very easy to do. my favorites are small needles stuck in the end of a pencil eraser.

close up the the beginning of the flower

These are the beginnings of some of my flower rings and starting to sprue them up.

another one finished

Spruing allows the wax to melt out of the mold and for the metal to get to your piece! not having enough sprues or having them in the proper location can cause your piece to not turn out.

flower ring w/ sprues

After all sprues have been attached its now time to weigh them. This if very important and is often forgotten. The weight of the wax is used to determine how much metal you will need for the casting. Because each metal has a unique specific gravity - you will need to know what number to multiply your wax weight by. For sterling, you can do it two ways - you can multiply by 10.4 and then add a half ozt (troy ounce) or you can simply multiply by 15. I usually do both to be on the safe side and figure something in the middle. For very small or very large, using teh 10.4 and half ozt is usually best.

make sure to weigh them!

After the waxes are weighed, its time to attach them to the sprue base or button.

on the button

Then the flask is lowered over the waxes. It is important that there is at least 1/4" of space between the edge of the flask and the waxes. Now believe me, I've pushed it and nothing bad has happened, but that doesn't mean that it won't. You can have a blow out where the hot molten metal breaks through because there was not enough investment. Same with the top of the flask, if the wax is too close to the top, the metal can break right through. And for vacuum casting, this could be very bad as the metal would most likely damage your casting table.

.. and in the flask

now you are ready to invest!

You need to know the size of your flask and how much investment you will need. For this sweet little flask, I only need a 1/2lb and 3.5oz of water. Measure the water out first and pour it in the rubber mixing bowl.

investment process.... the beginning

Now weigh out the investment. Investment contains silica - so you should wear a dust mask if you don't have exhaust. I got this cute blue scale for very cheap - and its blue! no need to spend big bucks on an expensive scale - it just needs to work.

weigh out investment

Set the timer for 8 minutes. This is the longest that your investment should be disturbed. Once it starts setting up, you don't want to be messing with it. I start the timer and then pour the investment in to the water. Mix for 3 minutes - right when it turns to 5 min, its time to vacuum.

set the timer

Vacuum the investment for 2 min - this is the first step in vacuuming.

vacuum pt. 1 - investment only

Bubbles are good - this is the vacuum getting all the air out of the investment


Now, pour the investment in to the flask. Its a good idea to have tape around the top of your flask to keep the investment from bubbling over and making a huge mess. When pouring, pour down the edge of the flask, not directly on the waxes as it could cause the wax to move slightly and perhaps against another wax or too close to the edge.

vacuum pt 2 prep

Now for the vacuuming of the flask! If you are vacuuming more than one flask of the same size, make sure to mark them. I use a piece of chalk to write a number corresponding to the wax weights - the chalk doesn't burn off in the kiln so its easy to distinguish when getting them quickly.

vacuum pt 2 - in the flask

This removes air that might have been trapped around the waxes and still in the investment from pouring - vacuum for approx 1.5 minutes - don't go over your 8 minutes.

It bubbles up and over like an ancient tar pit! The rings were pretty small in this flask, so I didn't fill it up all the way to reduce the bubbling over.

If there was a little bit of investment left over, after the time is up, pour the little bit on top. With vacuum casting, you need to leave at least 1/8 of an inch at the top to aid in the suction during the casting. if doing centrifugal casting, it can go over the top of the flask.

now it needs to sit for about 10 - 15 undisturbed until it sets up, then it needs to sit for about 1.5 - 2 hours before you can start the burnout process in the kiln.

bubbles again!

Once the flask is ready - it goes in the kiln and starts the burnout process. Burnout times are anywhere from 5 - 12 hours. The 5 hour burnout is perfect for just doing a couple of small flasks. Since I'm just a small time operation and didn't have the extra $900 to spend on an automated system, I have to manually adjust the temperatures to make sure the burnout process moves along smoothly. Hour 1: 300 degrees, Hour 2: 700 degrees, Hour 3 and 4: 1350 degrees, Hour 5: 1000 degrees - and hold.

in the kiln

Once the kiln has been holding at 1000 degrees for an hour, its time to start heating up the crucible and the metal. Make sure the crucible is red hot before adding the metal.

heating up the crucible

Once the metal has melted, give it a pinch of flux, a stir with a carbon stirring rod (and make sure to heat it up first or the metal will stick to it)

melting metal and stir

Note the hands free set up I made with some nice fire bricks!

makeshift extra hand

Now with my hands free, I can get the flask out of the kiln. Make sure to check to see that the pathways are clear - if burning out natural material, some ashes might be stuck. You can check it before you start melting the metal if you think there might be an issue you'd need to clear up, otherwise, a quick check on the way to the casting table is just fine. Also note the giant fireproof glove. I wish they made them in smaller sizes!

getting flask out

Place the flask upside down on the casting table (same as investing table, just make sure the toggle switch is flipped to "Cast") with the holes facing up. Turn on the vacuum pump.

turn on the pump

Position the crucible over the flask - make to always keep the torch on the metal. Removing the torch can cause oxygen to get in and that is bad.

starting to pour

As you are pouring, keep the torch on the metal and pour quickly. Pouring too slowly or moving the torch can cause the metal to freeze up and your casting won't work


Once the metal is poured, turn off the torch and the vacuum pump. Release the vacuum by flipping the toggle off of cast and move the flask away to let it cool. Wait until the metal is no longer red hot. I check it under a dark area of the table before quenching.

red hot in the flask

Now that the metal has cooled a bit and is no longer red (generally 2 - 5 minutes) it is time to quench. Make sure the flask is completely under the water. You want it to all be bubbling completely underneath the surface of the water. If you have used cast in place stones or some alloys you don't want to quench when the metal is hot. You need to let some completely cool up to an hour so as to not crack the stones or cause the metal to be shocked. Regular sterling is fine to quench after a few minutes.


These castings have been scrubbed clean of most of the investment, but there are still bits around the sprues and in the creases of the flower

another crusty casting

Soaking them in vinegar is a great inexpensive way to remove the investment and to clean the metal! I often leave them in there over night or longer depending on small detail areas. And its nice to have the metal clean already! It does take longer than an ultrasonic cleaner, but if you don't have the money or the space, vinegar works just fine.


And now its time to clean them up! removing the sprues, grinding, filing, sanding, adding texture to camouflage where the sprue had been, adding a patina, and the final polish all await your piece!


Kirsten said...

Thank you so much for sharing that. I've only done centrifugal casting and the costs to set it up are rather daunting.

Beth Cyr said...

Thanks Kirsten! I'd seen your comment and it spurred me to get this done finally! I was just about to let you know I had posted it!

I learned on centrifugal and that was what i wanted to get a set up for, but cost wise, it was more expensive b/c I still needed the vacuum. So, two in one was best. And getting the automated kiln set up was a lot more money too. ... and I was fortunate enough to have some help by way of a Christmas gift from my fiance.

Wendy said...

Holey Moley!!! What a cracking tutorial!

Catherine Chandler said...

That is a fantastic tutorial! Now I want a casting set up :)

miznyc said...

wow! great tutorial! It was fascinating to see what goes into the process of lost wax casting.

A Blond And A Torch said...

Terrific tutorial!

Tango K said...

Awesome tutorial! I love to cast, but don't have the set-up at home to do it. I really admire your working to bring this to the masses! Keep up the good work.

Unknown said...

Awesome tutorial! I was a metals major in college and I miss having access to all the equipment! It was nice to just see all those pictures again!

RuralAbandon said...

Well done! I do centrifugal casting so it was interesting to see how the two differ. I can only imagine how difficult getting some of the photos would have been if you didn't have second person there to take them!

Beth Cyr said...

Thanks Ladies!!
It was definitely one of the things I missed most about the university studio too, took me awhile to get the bare minimum, but its been so worth it!

RuralAbandon - I do miss the centrifugal and think that one day I'll get that set up again!

julie said...

that was a superb tutorial Beth! I almost feel like I could attempt something like that after reading it, I am kind of curious about the time you put into the flower wax looks intense.

Anonymous said...

Great tutorial!!
I'm interested in getting started in lost wax...and i was wondering if there is anyway to do this process w/o the vacuum. Or, is there any way to rig up your own vacuum set up?

Beth Cyr said...

i have no idea if you could rig up your own... the vacuum pump is really heavy duty - the vacuum is key in getting the air out of the investment and when casting, getting a complete casting. i forgot to turn it on one time and when i poured the metal in to the mold i realized i'd forgotten! the pieces kind of turned out, but w/ much much less detail. kind of like if I'd worked on getting great detail in the wax and then held it over the flame a little bit and the wax melted in and "erased" alot of the good detail. the general shape was there, but without the vacuum, no go. there are various ways to cast though, this was just the most economical since I wanted the vacuum for getting the air out of the wet investment to begin with. there is a little vibrating table thing that you can use, i've heard it doesn't work very well, and before they had vacuums, my teacher told me they'd just tap the flask with a spoon. but you'd still have loads of air mixed in.

hope that helps! :)

Anonymous said...

Great tutorial, I'm just getting into casting , have a spin casting setup, but am considering the vacuum route, and am surprised to see that you are using a standard flask, not a perforated flask set inside of a chamber, does it do as good a job on larger castings, and do you use any sort of venting?

Beth Cyr said...

i think b/c the flasks and pieces i'm doing are so small, it doesn't really matter. for awhile i was trying a wax web around the inside of the flask, but it was so much wax that had to burn out compared to the short burn out times i was using for my small pieces, it seemed to make it worse. I haven't had any problems at all. I've never used the perforated flasks either... so i have no idea what the difference would be!
also, not quite sure what you mean by venting?

Anonymous said...

Venting would be a thin wax wire out to the surface of the mold, from high points that might not fill if there is air trapped, but the investment must be porous enough that the air and gasses are sucked through it well enough. I was going to ask about the webbing, but you answered that. I'm thinking about using this method for belt buckles and small maquettes of my bronze sculptures , somewhere in the 1 - 2 lb area.

Beth Cyr said...

Oh wow! lovely!! thanks for the link to your site!
i thought that might be what you meant about venting - so the wax web basically acts like that. i'm actually planning on doing a belt buckle out of some shibuishi soon, so I might use the webs again for that one....

gixxerchic16 said...


I really want to get into metal casting and I was wondering if you could give me some hints or info on how to do it! I've looked through Rio Grande and looked at all the materials and what not, but still not sure where to start! I've seen some amazing pieces, especially with that shibuishi, and I really want to learn to do that too! So any info would be great!

Thanks, Brittany

Beth Cyr said...

Hey Brittany!

If at all possible, I would recommend taking a community jewelry class that offers casting - at least to get a good background. I'd been casting for years before I got my own set up and it was still nerve wracking to do it on my own!
However, if you have done it before and at least know the basic process and you have the money - no reason not to jump right in!

Feel free to contact me on my etsy site - or through my regular website - as posting here could be very lengthy! :)

talk to you soon!

gixxerchic16 said...

Hi Beth,

Unfortunately I live in Fargo, ND and there isn't any classes like that offered here, unless I go all the way to Minneapolis. :( Is there a good book or video out there that might work to help me out in getting started? And no I've never taken any casting classes before.

Thanks, Brittany

Deepak said...

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Casting Jewelry said...

Extremely thorough tutorial! The pictures were great and you explained every process very well, thank you. Nice ring by the way.

wedding ring said...

Thank you for such a great tutorial..I went through it deeply. You have explained very thing briefly. You are good trainer..Thank you !

Diamond Jewelry Florida said...

I find your post is very interesting. Thank you for sharing this tutorial. I'm also in the learning process. I get lot of information to start new thing.

bhupesh said...

Hi dear ,
when i withdraw wax from mold the wax
broke out . please help

Beth Cyr said...

hi bhupesh!
i'm not quite sure what you mean? when making a mold like I'm talking about, using a plaster like investment, the wax is burned out in a kiln and gone forever. this is the mold that metal gets poured in to and needs to be hot from the kiln when doing so.

if you are wanting a mold that can be reused for other waxes, you need to do some sort of rubber or silicon mold, which is not really my area of expertise...

hope that helps?

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GĂ©raldine said...

Thank you so much for taking the time to put this together! Most helpful tutorial out there for a jewellery student. Great tutorial and beautiful ring!