Lost Wax Casting

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About: I'm a full time jewelry artist and loving it!

This is a brief outline of my lost wax casting technique. There are several ways to cast, this is just the way I do it as a one woman show! Also, this was my set up about 7 years ago and some things have changed - I have a slightly updated longer version here on my website.

You can view a lot of my finished work at BethCyr.com or BethCyr.etsy.com

I use all sorts of random tools for my wax working. Most importantly, my fingers, and a tiny needle in the end of a pencil! I also made a little denatured alcohol lamp out of a baby food jar. The wax I use most of the time is a soft brown wax. It's my favorite.

If you're interested in getting your own casting set up - check out my supply list!

Step 1: Wax Work 1

The beginning of one of my flowers

Step 2: Wax Work 2

Another flower ring, almost finished

Step 3: Wax Work 3

This flower is all sprued! 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.

Step 4: Weighing Them Out

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 the 10.4 plus half ozt is usually best.

Step 5: Attach to Sprue Base

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

Step 6: Place Flask on Base

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.

now you are ready to invest!

Step 7: Set Up for Investing

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.

Step 8: Weigh Investment

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.

Step 9: Time It and Start Mixing!!

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.

Step 10: Vacuum Investment in Bowl

Now that you've mixed for 3 inutes, vacuum the investment for 2 min - this is the first step in vacuuming. Bubbles are good - this is the vacuum getting all the air out of the investment

Step 11: Pour Investment in Flask

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.

Step 12: Vacuum Investment in Flask

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. 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.

Step 13: In the Kiln!

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.

Step 14: Heat the Crucible

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.

Step 15:

When 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)

Step 16: Hands Free

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

Step 17: Get the Flask Out of the Kiln

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!

Step 18: Place Flask and Turn on Vacuum

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.

There is a small hole in the table that allows the vacuum to actually pull against the flask and create the suction needed to pull the metal in to the mold and every tiny detail of the mold - even fingerprints show up in the detail captured in the mold material. Pouring the metal in to the mold w/o the suction will result in loss of detail and loss of your piece. How do I know? I accidentally forgot to turn the vacuum on one time. The piece turned out, but much of the fine detail wasn't there. The vacuum is truly needed to get the metal where it needs to go - and fast!

Step 19: Start to Pour... and Pouring!

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. 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

Step 20: Cool It...

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.

Step 21: Quench It!

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.

Step 22: Dirty Casting... Clean the Investment Off

I use a toothbrush to get the bulk of the investment off.

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.

Step 23:

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!

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70 Discussions

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Moonflower_Jewelry

Question 7 weeks ago on Step 23

Hello,
I used to have a chart that told the amount of investment an water needed for different sizes of flasks. Does anyone know where I can get another or what book the information is in?
Thank you,
Angi

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RoseD18

2 years ago

Do you do castings at customers request? I have, well had, a pendant that was very special to me, and the company where it was purchased it isn't in stock. I am trying to find someone who could make this pendant for me, at a reasonable price.

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darrell26

3 years ago

Hey I'm getting ready to be in the business of making gold grills, could you please provide the steps you roommate did to acheive such quality work, thanks

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ZachariahH1

3 years ago on Step 23

Can you recommend a vacuum table to use for casting? I'm interested in making rings and such but have had issues with the detail not showing up. Vacuum casting seemed like a clear solution.

P.S.

Great tutorial!

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madmanmoe64

6 years ago on Introduction

From what I can tell the investment mould is destroyed each time to get your piece out.
If I wanted to cast multiple copies of an item can I use silicone rubber moulds to cast multiple wax masters?
I've tried pouring carving wax (not decent jewellers wax though) into a mould and it was far too thick.

3 replies

Yes the investment mold falls apart when you put it under running water or a large vessel of water which can be done about 30 seconds after the poured metal has hardened. If you are making a ring, or something small like this you have it out of the mold and are inspecting it within 5 minutes of heating the metal to molten; the process is quick.

To make multiples in jewelry making what is usually done is a rubber mold is made from a positive metal piece using heat time and pressure. With this rubber mold which has been either sprayed with mold release or coated with a thin layer of baby powder, molten wax is injected then the mold is carefully pulled apart and sequential, nearly identical wax positives are taken out. These wax pieces are cleaned up if required and often put together in a tree like pattern of sprews and mounted onto a rubber canister lid, put inside a steel canister and poured with investment.

If you want to make a repeatable mold of an object from nature like a bug or a leaf, one must first pour a plaster mold with investment, pour a metal positive from this and then make a rubber or silicone mold from that. if you wanted to make a mold of say a walnut, or something from wood or stone you may be able to cast the rubber mold directly from the object.

The rubber mold to make all the wax molds from, is made with a thick metal plate that has a hole in the center in the shape of a soft square and 2 thin plates that serve as end caps. laying the thick piece on top of one of the sheets of metal makes a container within which one builds up rubber sheets that are sticky on 1 side.along one narrow edge one inserts a turned triangular cone and a rod made out of brass, this will serve as your injection port and your sprew for casting. touching this sprew one adds the metal piece of jewelry to be cast with gems removed. small pieces of rubber fill any gaps created and then smooth layers of rubber cover the item so it is uncased within layers of stuck together rubber. there should be just a little too much rubber to ensure solid contact when it begins to melt... ( also note there are different types of rubber, primarily non shrink is more expensive but yields most exact results and there is a more standard rubber sheet which causes a small amount of shrinkage in the final mold.)

Then a top plate makes the rubber mold sandwich and the whole works is places in a heated vice where the vice is turned every few minutes as the rubber melts to make a tighter mold. after about an hour the mold is aloud to cool and all the rubber sheet has melted together.

Using a scalpel, the mold is carefully sliced down the middle revealing the metal positives.

From this the wax may then be injected and as myriad multiples of the small jewelry object can be made in wax to then be poured in investment, burned out, and poured with molten metal.

i don't seem to be able to arrange these attached images in a sequence but here are several images of mold making and pours i did using this process. the very last image is a lizard i found deceased in a pool skimmer so decided to honor its life with a death mask of sorts. the detail picked up by the investment was really amazing. Poor little thing.

The last row shows some grills my roommate made which involves even more back and forth mold making...ending in the lost wax process...so take an impression using either alginate or 2 part polymer clay. Alginate gets more detail but the mold dries quickly, so if using alginate immediately pour a positive using dental stone if using 2 part polymer you have a bit more leeway, some brands shrink more then others. but pour a positive of the teeth by making a little dam back at the molars. with the positive, put a mold release and build up with either dental wax and a flame and wax building tools or press thin sheet wax over the positive and trim with scalpels till desired shape add sprews and pour the investment.

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sokamiwohalisarah.nashold

Reply 3 years ago

sarah, how much would you charge to make a silicone wax mould for a ring I want made? pictured is the ring. I could send this very ring to you for the mould "blank".

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Hi there! So sorry for just responding - You can definitely make a silicone mold for making multiple wax copies. I prefer to make each wax individually (to make them all slightly unique) so I like the one time use. There are a lot of different mold types/materials. I don't make many so I'm not a great source of information on that topic... Most people use some sort of wax injector for their molds. I have a friend that uses a syringe and pipes it in to the mold that way. There are different types of wax for using in a mold though - with better flow most likely than just a basic carving wax.

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TaranS

3 years ago on Introduction

How did you manage to create such a fragile and intricate piece without it breaking, whenever i try to make a piece such as that it just breaks the wax (I use Green wax).
If its just my poor carving skills can someone link me to a tutorials to carving intricate details?

Thanks

Whats the vacuum machine called by the way?

I've been thinking about doing this for a while now and was hoping to get some gear together.

Great tutorial btw :)

1 reply

It is actually fairly easy to make your own vacuum chamber and kiln - take a look at the way I did my engagement ring (https://www.instructables.com/id/Casting-Rings-From-Startup-to-Finish/).

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rabiddream

4 years ago on Introduction

Out of all the tutorials I have been looking at on the lost wax casting process, yours has been the clearest and most helpful of the process from wax to finish. Thanks much!

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E86HotWheels

4 years ago on Introduction

Safety eyewear is important. From the torch pics, it's clear no safety eye wear is being worn. Visorgogs are inexpensive and provide splash and impact protection. They can be found on amazon. Your eyes cannot be replaced. Accidents are called accidents for a reason. If we knew they would happen, then we wouldn't have them.

The tutorial is well done otherwise. Safety is important.

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TheStudio7

5 years ago on Introduction

Wonderful. I am definitely going to try this. Thank you for sharing.

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deth2all

5 years ago on Introduction

I made a lil video of me making a few things , Great instructable by the way, Very detailed .

https://www.instructables.com/id/Lost-Wax-time-lapse-silver-casting/

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Gilligan92

6 years ago on Introduction

This is a great guide to lost wax casting and I really enjoyed it. I do have one question though. How do you determine how much metal (in my case white gold) you need by the weight of the wax? What is the equation I need to use? Thank you for the great instructable and your time.

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bcyrjewelryGilligan92

Reply 6 years ago on Introduction

Hi there!
Each metal has a conversion factor - the "specific gravity".
I use this chart on the H&S site since there is where I buy my metal.
Standard nickel white gold in 14k is 12.7. Which is different than 18k or palladium white gold.

https://beta.hooverandstrong.com/casting-grain-specifications

There is also a phone app I have that does conversions called iMakeJewelry.

Multiplying the wax weight by the specific gravity will give you the metal needed for the piece. Then you need to add extra for a button. My buttons for gold tend to be a lot smaller than sterling - especially with vacuum casting - generally around 4 - 6dwt depending on the size of the piece.

Hope that helps!! Let me know if you have any other questions!

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blindpig

9 years ago on Introduction

Have you considered "steam casting" as an inexpensive alternative to vacuum casting? It is a more primitive method but requires less expensive equipment. Might be considered for experimental lost wax casting trials. Would allow trying the process without buying equipment first. Adding equipment later always an option.

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brianlacyblindpig

Reply 6 years ago on Introduction

If you have a sec - would appreciate any news / tips re process and gathering tools to do steam casting. send to bridlacy at gmail.com - w my thanks!!