After successfully mixing 300# of sodium silicate bonded sand this weekend, I was moved to try making a pouring cup mold set, a wooden box with a 3D printed insert, and mold it . I used mortar mix sand and 6% N/lab grade/40% sodium silicate plus 10% of that weight in propylene carbonate. This all seemed in line with Rocco's video and Cobett's notes in the 'monograph'. I tried de-molding 1.5 hours later and there was little adhesion in the sand. I did find a few resin balls that had hardened. Wondering if I just need to up the % of sodium silicate and PC until it works? The PC is from 2023 and a small amount was used for K-Bond and the SS is from 2024 but unopened until today. Thoughts? I was also going to try an epoxy bound set as well. I added the PC to the sand in a large plastic kitchen storage bag, mixed, then added the SS. ... 719 g Sand mold capacity +5% 43 g 40% SS at 6% 4 g Propylene carbonate at 10% SS (used more like 5g) ... 719 g Sand mold capacity +5% 28.77 g Epoxy mixed at 4% Ironsides' recipe pointy sand 23.02 g Resin 4:1 + 5.75 g Hardener 4:1 ... -the Tom Cobett monograph on cores, http://jarod.eells.us/projects/FoundryEquipment/sodium-silicate.html (edit) also captured as a file here: https://forums.thehomefoundry.org/i...-silicate-for-core-making-by-tom-cobett.1334/ -Rocco's video and Ironsides' epoxy formulas: http://forums.thehomefoundry.org/index.php?threads/replicating-a-motorcycle-intake.1916/
I did a mix at 10% with not much differing results. I am staring to suspect that my propylene carbonate is bunk. a. sodium silicate left in the yogurt cup become hard in plain air all by itself b. various clusters of sand are bound together after sitting open to room air c. a spot doped with propylene carbonate did not accelerate, ball up, or harden...it just looks oily d. (not shown) K-Bond type oil-bond sand using same propylene carbonate has a 'greasy' feel and texture as cast https://forums.thehomefoundry.org/i...-k-bond-sand-similar-to-petrobond.1759/page-3 I tried hitting the Dixie cup of mixed sand above 'c' with 25% CO2 (MIG welding gas) in a plastic bag around the nozzle before I doped it with PC. There was no change. Is 25% CO2 normally enough to set SS?
Yes, apparently. 50g sand 4g 40%SS gased with 25% CO2 in a puffed-up Ziplock-style bag off the welding gun nozzle, minding the ground clamp and wire) The bottom 1/4"(6mm) did not harden but the rest turned out.
Here is what the Navy has to say about CO2 sand. And we use pure CO2 from a welding cylinder regulated down, i dont recall the pressure , you need to force the CO2 into the sand, we had an air gun with what looked like a 3 inch plunger on the end, place it on the mold hit it for a couple of seconds it would harden the sand 6 inches deep I have no idea what the Propylene carbonate is for??? the only thing we added to CO2 sand was Sugar and corn flower for collapsability
Thought it was only 1% of the propyline carbonate. Too much and it does not work. Found that out with the accuset I use....
Thanks. The propylene carbonate is supposed to make the sodium silicate kick/harden without CO2. Good questions. The Corbett paper says 10% of the silicate. That lines up up with the Silbond I used a couple weeks ago, those harderners were 10% of the resin (sodium silicate) and resin was 4% of the sand. If more is not better I may have skewed my own results as I was never shy mixing in the PC...
I may try working brackets 10% to 1%, like 10g sodium silicate and 1, .8, .6, .4, .2, and .1g propylene carbonate. I mixed and molded the epoxy version tonight, will demold in the morning.
My bad!!! I looked up the catalyst pdf and it is 10% of the weight of the sodium sillicate... But also know 100% that if you mix too much in it will not harden.. So yea, Taylor it back slow and see what you get... I'm also unsure how much temperature has an effect on it...
Thanks @DavidF I found some PDF's about Accoset here: http://forums.thehomefoundry.org/index.php?threads/accoset-sodium-silicate-binder-and-catalyst.1341/ The epoxy-bound pour cup is stuck in the mold. It was waxed heavy but I forgot to dust it with anything. I will try to work it out after another cup of coffee.
Mold is worse for wear but the epoxy-bound sand is out. Thinking of just pouring this in aluminum for a more durable pour cup inner plug. When I was molding these at the iron pour, the pattern inner was usually attached to a base board that had wood strips to align the sides (sides being attached to each other but not the base) keeping thing in register. The sand that was on top as molded is a bit loose, as if the epoxy drained a little. The bottom is solid including the surface against the plug.
