CASTINGHOBBY FAQ
(Frequently Asked Questions.)

Back to Table of Contents



Molding Sand

Molding sand is more than just sand. Typically it is a fine grade of sand (mine is 110 grit sand blasting sand), clay binder and something to moisten it. There are two types of molding sand of interest to the casting hobby.

Water bonded sand

Water bonded sand or Green Sand has been around forever and is the traditional molding sand. It is made with fine sand, Bentonite Clay and water.

NB: Bentonite clay is not the only binder available for making green sand. There are other 'flour' types available, though for the home/hobby foundry Bentonite is probably the most common.

Oil bonded sand

This is a LOT different. Commercially sold as Petrobond and homemade as K-bond. Fine sand is combined with Bentone Clay, oil and a Catalyst. If You're in a hurry to get casting/ want excellent results / have the budget, use Petrobond.

Petrobond is available in at least two forms - Pre-mixed and binder / catalyst to which you mix your own sand.

Petrobond is re-usable, HOWEVER, you will need to obtain or construct (self constructed being the far cheaper option) sand muller. A sand muller is basically a mixing machine that 'squeezes' all the sand thoroughly so that all grains of sand are evenly coated with the binder.

Petrobond is very 'sticky' and will hold shape very well, provided sufficient draft is allowed. Having said that, I have found that slightly less draft is required for oil bonded sand. Wear disposable gloves when working with oil bonded, as it WILL stain your hands, as well as pretty much everything it touches.

Another very good property is the very detailed surface finish oil bonded sand will give you. I would estimate a 1000% improvement over green sand.

The difference is in the clay. Bentonite is common and cheap and absorbs water. Bentone is a little pricier and absorbs oil.

Don't make the mistake of using kitty litter to make green sand. It makes a mess. Some report success, but many others have had to bury it.

for the FAQ
Something I have seen with PB II is if it doesn't seem to work or look quite right I add a little "heat" (PB II does not use a catalyst so I don't know if this method will work on PB or Kbond) and after mulling it acts right till the "heat" evaporates then you have moisture. basically moisture makes it act dry and when you get enough oil in it to ram it will be sticky. in my case I had it happen twice the first autumn I would go out to the shop after it had started warming up for the day humidity around 50-60% and every thing in the shop was cold from the night before, just like that can of "_____" you pull out of the fridge, condensation. the second time it happened I bought sand after one of Oklahoma's famous rain storms and it was wet. With all that said, a muller may not be a necessity but it does make experimenting allot easier
Leon in Luther Ok.
http://community.webshots.com/user/lrisen
http://www.myspace.com/punkinspatchrr


Targeted FAQ

Whatis the difference between Organo-Bentone and Bentonite? Are they similar? billblackburn@xxxxxx.ca

Bentonite is the base clay that Bentone is made from. Bentone is treated to bond with oil. Bentonite naturally bonds with water. Ray Brandes


Have you tried synthetic 2-stroke oil instead of the real Polybutane?  billblackburn@xxxxxx.ca

I use synthetic two stroke oil all the time to 'freshen' and in the winter when just a touch more oil is needed. As my K-Bond pages states, Penzoil two-stroke oil is what I use. New K-Bond is made using Indopol from BP, but any SMOKELESS two stroke oil will work. Indopol is thicker than molasses in February, but the two-stroke oil is thin and incorporates easily.  Ray Brandes


To be moved to the metals page later


Other than having to be hotter, is Bronze any harder to work with than Aluminum?  billblackburn@xxxxxx.ca

Aluminum has a lot of surface tension so when you pour more head (tall sprue) is better than short if you have thin sections. Brass and bronze alloys behave differently. Some pour like lead and others develop a heavy skin and need to be poured hotter. Berilium-copper added to the melt just before pouring makes the metal flow better. 

For bronze, use Everdure, a silicon bronze. I get it from Atlas in Colorado. If you order from them get some berilium-copper shot too. You can also use berilium-copper welding rod cut into small bits.  Ray Brandes

http://www.atlasmetal.com/