[Note: these are my notes on making platforms/boats /art for the Ephemerisle festival (http://ephemerisle.org). This is just a "capture" post, intended to collect the information. No attempt is made at organization, grammar, etc, which I intend to do for a future post.]
Preparation of Silicate of Soda - Gossage
prepares silicate of soda or silicate of potash by fusion, much in the same way as that adopted in the production of ordinary glass. He mixes together about equal parts of dry carbonate of soda and clean sand, to which is added one part by weight of ground coke or charcoal for each nine parts by weight of carbonate of soda. This mixture is melted in the same way as mixtures of sand and alkalies are in glass-making. The melted mass is afterwards poured into cold water, which renders it more friable. The product is then ground to a fine powder, and afterwards dissolved by boiling in three or four times its weight of water. During the boiling liquid caustic soda is sometimes added. After reposing for a few hours the clear liquor is drawn off and concentrated by evaporation until it assumes a viscid condition suitable for mixing with pure soap.
Preparation of Silicate of Potash. -In making silicate of potash, twelve parts of dry carbonate of potash, two parts of sand, and one part of coke or charcoal are mixed together, and the whole melted and treated as above. In place of sand, ground felspar may be used, in which case three parts of this mineral are substituted for two parts of sand, and only one-half the quantity of alkali is used.
Sulphate of soda or sulphate of potash may be used instead of the carbonates of soda or potash in making the "soluble glass," in which case three parts of either sulphate are substituted for two parts of either carbonate, and four times the quantity of coke or charcoal above given.
http://ferrocement.net/ferro/msgdisplay.php?mfm=viewmsg&id=05485
The 15-ft-wide decks of our 55-ft Valeo series boats contained 1-ft x 2-ft x
1-in-thick blocks of rigid urethane foam sandwiched between one layer of
3.4# expanded metal lath and 1-in x 1-in 14-gauge welded wire fabric. Shear
ties are placed around the perimeter of each block to hold the upper and
lower laminate together. In marina floats that are too small for persons to
work inside, we laminate any type of mesh over blocks of expanded styrene
beads. Laminates can also enclose cores of styrofoam, perlite, paper, saw
dust, or other filler material bonded with waterglass or another adhesive
compound.
Concrete mixing tip
http://concretecountertopsupply.com (Fishston)
2 sand 1 cement
pva fiber
csa cement - 10 - 20%
citric acid (slows down set of CSA cement)
meta kaolin
Dayton superior - acrylic bonding agent J40 - can be used straight or 1:1 water (3:1 water:bonding agent); eliminates need to water cure concrete); makes concrete more water resistant; increases strength of concrete (52% solids)
Super Slump Buster (methylcellulose) - thickens water; 8 oz / four cubic yard
Acryl 60 is available at Ace Hardware - 45% solid
Kongcrete - ships powder
2:1 sand:metakaolin
2-3 minute mixing time
Great blogs - David Neat - Makes models.
https://davidneat.wordpress.com/styrofoam/
Cardboard sealants
Ames Block & Wall Liquid Rubber
Redgard
Paper drywall tape
Titebond III glue + cloth mache
Waterpoof cloth
16oz of beeswax
8oz of turpentine
8oz of linseed oil
Glidden Gripper + fiberglass cloth + xps foam furniture
Flexbond concrete + paper + exterior high gloss enamel
http://www.diyeasycrafts.com/outdoor-weather-resistant-paper-mache.html
How to cut hardiboard
How to make a life-size sculpture of a baby elephant
http://www.ultimatepapermache.com/elephant-sculpture-video
Expanded aluminum - good for reinforcing thin sculptures (elephant ear; normally used to
Joint compound + cellulose insulation + marine varnish
How to make a foam hot wire:
"The idea of a dimmer and transformer didn't make sense to me and didn't work for a lot of people, so I went with a car battery charger with a 2A current limit setting. This worked, but the guitar string broke after about 30 seconds. I tried 3 different strings of different gauge and composition with the same result. I finally got some 22 gauge nichrome wire. At 15 inches it is 1.1 ohms cold. At 2A this would be around 4.4 watts (W=I^2*R), which doesn't seem like enough, but actually it gets plenty hot and works fine. I vaguely remember that light bulb resistance goes up by around a factor of 10 when it heats up. Maybe that's what's going on - a 44 watt light bulb would be plenty hot. Probably a much lighter gauge would work fine as well, but may not be as strong. The wire does get loose with heat. Instead of the ingenious tensioning method described, I used a guitar tuner, which I can tighten when the wire heats up and loosen after using. This thing cuts through styrofoam like butter."
"Ohm meter is your friend, measure resistance of wire, you take the voltage, divide by the resistance and you have the amps of power that will flow through wire. Make sure your power source/transformer (and fuse) is rated for higher than that to avoid wrecking transformers.
SO for example if your wire has 6 ohms of resistance, and you have 12 volt power source, you need about 2 amps of power. voltage may go a little higher, eg 14 volt in reality, so have safety margin."
I use an old AAA battery charger, 120AC in -> 12DC 1A out and nichrome wire (#30 AWG) over 12" - no dimmers or pots, no probs,heat just right Han transformer doesn't even get warm. I also use same xformer and wire on a vertical machine and a horizontal machine and it works perfectly.
Tips - use nichrome wire, 26 - 30 gauge. Its heat tolerant properties are mentioned a lot but is not is its resistance qualities. On a machine where a guitar string would overheat, nichrome of similar gauge often barely gets warm. All around easier to work with and its dirt cheap in100ft spools at Amazon.
As already suggested, put a small lamp in series. Both a pwer indicator and (if you select a bulb rated between target output and transformer rating you've got a poor mans fuse as a bonus.
For power shoot for the 12 - 24 watt range (I have good luck at >7VDC. A trickle/slow charger for 12Vcar batteries (cheap at WAlmart12VDC/6VDC at 2A is effective). You can also find the wall type cheap at goodwill.
Unless you require a lot of fast and heavy stock removal you'll get better results at just enough heat to cut and you'll generated much less nasty toxic smoke. The trick is to learn by doing what force and power yield what results in smoothest most accurate cutting.
To calculate the variables ref the Jacobs calculator already mentioned.
For a power supply, I just used an old ATX power supply from a dead Dell PC. Using NiChrome wire and this calculator : http://www.jacobs-online.biz/nichrome/NichromeCalc.html
I was able to get very close using the calculations alone and fine tuned it from there. I am using 10.4 inches of wire at 5vdc and it hits 620F along the length of the wire. Perfect cutting temp on everything from 1/8" sheets to 8" blocks. Consumes a touch over 2A, which is well within the 27A the PSU is rated for on the 5v rail.
Fiberglass and resin suppliers may have cheaper sources of XPS foam than building supply stores.
Use Vaseline mixed with ultramarine powder pigments as a mold release.
Thompson's waterseal can be used to seal concrete, cardboard
