INVESTING A WAX PATTERN FOR BRONZE CASTING
N.B.  Investing works best if you use a team approach.  Two people are the minimum needed, but three or four is much better. 

These directions assume that you already have gated your pattern.

MATERIALS AND TOOLS
FLASK MATERIALS: chicken wire – roofing felt – duct tape – 22 gauge wire
FLASK TOOLS: measuring tape – scissors or mat knife – wire snips – diagonal wire cutter – pliers
INVESTING MATERIALS: plaster – sharp sand (play sand) – luto – water – 8 oz. foam cup - alcohol
INVESTING TOOLS: bowl for mixing plaster - measuring buckets – holding buckets – mix bucket – mixer – putty knife – hammer – cold chisel – air blast - brush – diagonal wire cutter

PROCEDURE
The investment material for this procedure is made from a mixture of #1 molding plaster (plaster of paris), sand (play sand from Lowe’s), luto (old investment that has been ground into a powder), and water.  The ratio of materials is:
Plaster ----- 1 part
Sand ------- 2 parts
Luto -------- 2 parts
Water ----- 1 7/8 parts (a little less than 2 parts)

STEPS
1.                 Hand mix a small batch of investment, and, using the foam cup, cast a block of investment.  This will be used to support the pattern when pouring the investment.
2.                 Measure the height and width of your gated pattern.  Add to the measurements 2 to 3 inches to the width, and 3 ½ inches to the height. 
3.                 Multiply the width times 3.14 (3 1/7^th ), and add 6 inches for overlap.  The result is the length of the pieces of chicken wire and roofing felt you’ll need to make your investment flask.  The flask’s height is the same as the pattern plus 3 ½ inches. 
4.                 Cut out pieces of chicken wire and roofing felt to the dimensions you’ve calculated. 
5.                 Roll the chicken wire into a cylinder with a 6 inch overlap, and fasten with wire (or extensions of the chicken wire itself) at the top and bottom with fasteners in between at about 3 or 4 inch intervals. 
6.                 VERY IMPORTANT – Use your pattern to check for proper fit inside the cylinder.  There should be a minimum gap of 1 to 1 ½ inches between the sides of the pattern and the cylinder sides.  The cylinder should be as high as the gated pattern standing on the block of investment you cast earlier. 
7.                 If the pattern fits properly, roll the roofing felt around the chicken wire cylinder.  (Make sure that the bottom surface of the flask is even so that it will seal to the floor properly.)     Fasten the roofing felt with circumferential bands of duct tape.  The bands should overlap at their ends by 4 or 5 inches. The lowest band of duct tape should leave about 2 inches of the roofing felt exposed at the bottom of the cylinder.  The bands should be spaced about 8 inches apart. 
8.                 (Optional) cut a circle of roofing felt that will fit inside the cylinder. 
9.                 Seal the flask (that’s what you have just made) to the floor with plaster.  (Make sure the floor you are sealing to is clean and free of dust.)  the plaster seal should come up the side of the flask about 2 inches, and extent out from the side about 2 ½ inches. 
10.             VERY IMPORTANT – wait until the plaster seal is COMPLETELY SET before pouring investment. 
11.             Wash (brush) the pattern with alcohol to remove surface grease as an aid to making the investment adhere better. 
12.             Prepare however many holding buckets of dry investment you think you’ll need.  Follow a set pattern in putting materials in the buckets.  That way, if a mistake is made, it will be obvious, and can be corrected.  Put the luto in first, followed by the sand with the plaster last. 
13.             Place the cast block of investment in the flask (broad end up), and set the trap end of the gating system on it.  Check to see that the pattern is properly centered in the flask – make any necessary adjustments.  Block the open end of the pouring cup with wet paper toweling.
14.             A team member will have to hold the pattern in place while the pouring takes place.  If possible, this person should be seated away from the side where the pouring will take place. 
15.             MIXING INVESTMENT – One person using the power mixer, and pouring investment while another brings dry investment to be mixed and makes up more dry investment if necessary. 
16.             Put water in the mixing bucket, use the mixer to agitate the water, add the dry investment while continuing to power mix. 
17.             Continue until the mix is smooth (about 2 minutes) – don’t take too long, the mix thickens appreciably after about five minutes. 
18.             After the initial power mixing, check the investment by hand (take the power mixer out before you do this!).  If the mix is thorough and free of lumps, proceed to the next step.  If not, power mix some more. 
19.             Start investing the pattern by pouring the mix into the flask.  IMPORTANT - The mix is heavy and can break the pattern apart or shift it out of position. Avoid pouring the mix directly over the pattern or pouring from only one point in the flask. 
20.             If you’ve mixed 40 or 50 pounds of investment, you may find it easier to pour by using a bowl to pour smaller amounts than a whole bucket full.  An alternate method is to have the person who is holding the pattern in place their hand over the top of the pattern with their fingers spread apart – the mix is poured over the hand which breaks it into a several small rivulets, and spreads it around the pattern. 
21.             After each batch is poured, agitate the mix in the flask.  This helps to break bubbles that might adhere to the surface of the pattern (bubbles cause lumps on the surface of the cast), and helps ensure that fine detail is properly encased. 
22.             Usually, after the third or fourth batch is poured, the earlier batches have set enough so that the pattern no longer has to be held in place.  N.B. this doesn’t mean that it should not be protected from poured investment. 
23.             Continue adding investment in this manner until the flask is filled.  That is, the investment is almost to the top of the pouring cup.  The top of the cup, and the vent assembly should just clear the surface of the investment. 
24.             Once the investment has set, the sealing ring of plaster at the bottom is broken away using a hammer and cold chisel.  The duct tape band are cut at the overlap joint, and the roofing felt is stripped away. 
25.             Any wire projecting from the top of the investment is cut away, the foam pouring cup is removed, the vent hole is cleared, and a channel is cut between the pouring cup and the vent(s). 
26.             Carve your initials on top of the investment then use an air blast or brush to remove any loose crumbs of investment. 
27.             Transport the investment to the burn-out kiln.