Mixing up K-Bond Sand (Similar to Petrobond)

Discussion in 'Sand Casting' started by Melterskelter, Jun 9, 2021.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Here is a vid of the resulting castings:
    BTW, toward the end of the video I misspoke saying “methanol” meaning to say “ethanol.”

    Last edited: Jun 12, 2021
  2. Melterskelter

    Melterskelter Gold Banner Member

    Here is the post-pour smoke comparison. I notice the Kbond produced some flame—-is that the ethanol burning? I’m thinking it is likely.

  3. rocco

    rocco Silver

    Nice, fantastic results! It'll be interesting to see what the next batch of K-bond with the smokeless oil and glycerin is like, I wonder if it'll be flameless as well as smokeless.
  4. Melterskelter

    Melterskelter Gold Banner Member

    Here are 3 closeups of the castings allowing some comparison of surface finish between Petro and Kb. The upper two are Pb and the lower one Kb.

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  5. Tom Cobett

    Tom Cobett Silver

    I have a fondness for this group because I started in this business as a Home Hobbyist. At the age of 12, I started melting type metal, a mixture of Lead, Tin and Antimony that was use to make cast type for printing presses. I poured it into cast iron molds that made toy soldiers and fishing sinkers.
    At 14, I made my first sand casting in a Shop class at school. The rest us history. I’ve been in this business for more than 50 years. I have learned what works and what does not work.
    I will do my best to answer your questions on a timely basis.

    Tim Cobett
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  6. Tom Cobett

    Tom Cobett Silver

    That should be TOM Cobett!
    Fat fingers!
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  7. Melterskelter

    Melterskelter Gold Banner Member

    So glad to see you here,Tom!

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  8. Melterskelter

    Melterskelter Gold Banner Member

    Tom, one thing that puzzles me about the “catalyst” (I thought they were solvents) like Methanol, Ethanol, Propylene Carbonate, and now Glycerol used in the Oil-bonded recipes: what is there activity in these formulations? What are they doing? Their small percentage in the formula seems to have outsized effects.

    Second, when I use glycerin in the K-bond formula, do I use it in the same weight-based percentage as was recommended for methanol?

  9. Chazza

    Chazza Silver

    I would like to thank you Tom, for your contributions to my lack of knowledge on how to make cores. I am making good progress in making cheap cores, using molasses and corn-flour, thanks to you,

    Cheers Charlie
  10. Melterskelter

    Melterskelter Gold Banner Member

    This morning I used the more expensive “Smokeless” Lucas brand 2-cycle oil and used Glycerol (glycerin) as an “activator.” For 50 pounds of 100 mesh Olivine I added 1.5 pounds oil and 3 pounds of bentone plus 1.6 ounces of glycerin. This produced a sand with a very similar feel to the prior mix I made using the same weight of ethanol. It molded very easily and had the consistency of heavy cookie dough. The resulting casting from it give up nothing to proprietary Petrobond. I think the finish was just a bit better on the Kbond.

    As far as smoke production is concerned this Kbond was much better than Pb but no better than my other batch made with cheap 2-cycle oil (see above) that did not claim to be smokeless. Maybe the cheap oil is also specially formulated to be smokeless but just did not print such on the label. Or maybe the need for using smokeless oil is not so great. Hard to say without a lot more testing which I am not inclined to do.

    This is the oil I used today:

    Here is a vid of the pour. The Kbond is the center flask this time.

    And a few pics too:

    The K-bond casting is on the lower left below.

    The K-bond is the center casting below.

    K-bond is the center casting.

    My impressions (conclusions ?) so far are that the K-bond clearly smokes less than Petrobond when formulated with two different 2-cycle oils. Glycerol used in the same proportion as recommended for methanol provides a usable bonded sand. K-bond using 100 mesh Olivine results in a sand that molds as well or better than Petrobond and provides a finish as good or better than Petro.

    The biggest impediment for using K-bond may be the evident difficulty of buying Bentone both in adequate quantity and at a reasonable price.

    Last edited: Jun 13, 2021
  11. HT1

    HT1 Gold Banner Member

    am I noticing the the K bond molds remain flaming much longer then the P-bond molds, when they go out do they start smoking???
    and are we going to see some molds done in reused sand , just wondering if they results will stay the same /

    I'm seriously considering switching from 30Weight to a smokeless synthetic oil, though I have to wonder is Synthetic oils will have some additive that may cause issues over time

    V/r HT1

    P.S. Again thank you for the great knowledge
  12. Melterskelter

    Melterskelter Gold Banner Member

    It is true that the K-bond flames more than the Pbond. I, of course don't know why, but wonder if it is the alcohols in the formulations I have been using that are burning. I suspect that is the case. Evaporation of glycerol should be much less over time than methanol or ethanol as pointed out by Tom Cobett. For future mixing of K-bond I will be using Glycerol.

    When the flame goes out there is some smoke seen on the K-bond though it is still a lot less than with Pbond and it seemed to make kno difference which of the two-cycle oils I used.

    I know of no reason to suspect more trouble with synthetic oils than conventional oils over time. In fact, because synthetic oils big claim to fame is increased stability with heat exposure, I would expect less trouble. The only proof will be in using them long-term, of course.

    I have no practical way or particular need to segregate the K-bond from Pbond. The reduced smoke is nice, but not a big enough deal, in my case, to make me retire 200 pounds of Pbond and replace it with a like amount of K-bond. My plan is just to mix the two together so I have a little more than 300 pounds of working oil-bound sand. One thing is that I do not now fear degrading the Pbond by commingling the K-bond with it. All things being equal, I wish I could jsut use K-bond exclusively based on my experience so far.

    I am hoping other folks will relate any experiences they have making K-bond so we can add to the general knowledge base about this sand.

    I am hoping Tom will chime in on any of these issues as he is the guy who really knows the K-bond. I am a rank beginner.

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  13. Melterskelter

    Melterskelter Gold Banner Member

    Tom will be back here as soon as he gets his password straightened out. Some sort of glitch that is taking a little time...

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  14. Tom Cobett

    Tom Cobett Silver

    Smokeless 2-stroke oil will ALWAYS be better than regular (smoke producing) motor oils. You can also use mineral oils (white oils) but they tend to burn out at lower temperatures. Amorphous polybutene (a.k.a. INEOS Oligomer INDOPOL L-14) is better than smokeless 2-stroke oil, but hard to find in small quantities. It is completely smokeless and is considered to be a food-grade lubricant.

    The K-Bond sand will turn gray and eventually black after many uses. If it feels dry, add more of the oil component. If it feels lifeless (low in strength) add more of the glycerol or other polar compounds like methanol or even water. I don't use water since it causes steam in the mold. I don't want water anywhere near molten aluminum since it can cause hydrogen pin holing.

  15. Melterskelter

    Melterskelter Gold Banner Member

    A few questions were raised while you were off-line with password issues. If you have time at some point your thoughts would be of interest to this forum. They were:

    1)Would you expect any difficulty from commingling Pbond with K-Bond?

    2)Would you expect synthetic oil to be more or less stable than standard oils.

    3)Would you expect K-bond to mold any better or worse than Pbond?

  16. Tom Cobett

    Tom Cobett Silver

    1. You can mix PetroBond with K-Bond without expecting any problems. They use the same binder system.

    2. I would expect synthetic oil to last a little longer than non-synthetic oil. I would also expect that both of them will create some carcinogenic compounds once they are partially burned. That is one of the reasons that we had to stop using motor oils in the sand at Kent State University.

    3. Well prepared PetroBond and well prepared K-Bond should perform about the same from a casting quality standpoint. The grain fineness of the sand is probably has more influence on the casting surface finish. I would use sand that has an AFS GFN of 100 to 130.
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  17. Lou

    Lou Copper

    Wow, now I feel silly, Tom's on this forum already!
  18. Tops

    Tops Silver Banner Member

    Working on my first batch:
    50# sand, Covia 5030 (130 mesh) full bag
    3.25# bentone (from forum member Mach)
    1.5# Castrol 2T Super Snowmobile https://www.oreillyauto.com/detail/...-snowmobile-oil-2t-formula-1-quart/cas9/12150)
    .125# Denatured Alcohol (same as I use for stove fuel on the boat)

    I am at the 'cookie dough' stage, having just added the alcohol. Since I am using a mostly unmodified concrete mixer with a round stone, the mixer is either compacting on the inside if angled in or waterfalling nicely inside the mixer but spitting bits out the front if angled one more notch out...It seems a bit sticky on the hands compared to P-Bond. If this persists, would it make sense to add a little more bentone? Recipe would allow 3 to 3.5 pounds. I was going to leave it overnight and mull again tomorrow before messing with it. I ran the mixer with a plastic bag over the opening while mixing sand with clay and also while adding the oil, seemed to do well controlling the dust along with wearing a mask. Everything but the sand was weighted on a scale.

  19. Melterskelter

    Melterskelter Gold Banner Member

    Before making any changes I'd just use it some and see how it works. I'm betting it will be fine.

    You can use any ______ol as a polar agent. Glycerol is nice as it is a heavier molecule and does not evapoerate nearly as fast as light alcohols like the ethanol you used and I also used at first. You can get a gallon of glycerol pretty cheaply online. (It is a common component of cough meds. If you taste it (good) you will recognize the flavor and mouth feel.)

    While bentone does contain some silica dust, the association of silica dust with lung cnacer has only been seen in long-term intense exposures like quarry workers. Incidental exposure probably has far less health risk associated than does crossing the street after looking both ways in a crosswalk with the walk sign giving you the OK. I guess you'll never go wrong wearing a mask. But, I wish that it was required when a warning label is mandated on a product that also required was a clear understandable statement of relative risk involved. Not doing so is not very helpful and can have all kinds of unfortunate consequences.

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  20. Tops

    Tops Silver Banner Member

    Thanks Denis. I gave it a try this morning (squeeze and break) and it feels less sticky than last night and now brushes cleanly off my fingers. Onward!

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