Hello Everyone, I am new to the forum and I'm looking forward to gaining more knowledge and improving my skills with help from all of you, thank you! One of my recent projects has been a pendant in brass that has a negative space in the center that I have trouble getting the sand to stay put. I've attached a picture of the casting master (is that what they're called?). The master is made from carving wax because that's the fastest/easiest method for me to make them quickly. I have tried a couple of things to get the sand to stay in place in that central negative area that looks like a person: packing the sand super densely, tried to get the sand to split half and half, using little things to pack the sand as densely as possible in that space all of my attempts failed. I got as close as I could with the half and half method but still ended up having to cut out a lot of excess metal in the center. One thought I had was to leave a very thin "membrane" like layer in the center as possible to give the sand something to be packed against. I hope my description is good enough to give you an idea of what's been happening. How do you all pack sand for smaller items like this? I greatly appreciate any help that you can provide! Teo
The master is usually called a pattern. Does the person shaped hole have draft (taper) on the edges that would be vertical when you are ramming up the mold, to make it easier for the pattern to release from the sand? If so, could you give it a little more? That might help. Good luck! And welcome to the forums. Jeff
You have to have proper draft to get that pattern out of sand . you have probably rounded the backside of the pattern and that is backdraft, I almost always attache patterns to a board and then carve with an angle so back draft becomes way less likely . OH and try rubbing that part( pattern) down with graphite powder , you wont need much it will make it slip out of the sand V/r HT1
Welcome to the forum. I think trying to pack the sand in that tiny person space will be futile. My suggestion is to make a person shaped core and place it in the buffalo impression. You would need to fill in the center space that you have now, make a sand mold of the buffalo, and then place the person core in the center as you intend. The core can be made using sodium silicate, SS, or a baked core. The easiest way to shape the person core would be to make a rectangular core and shape the person by sanding the core piece with a fingernail sanding board.
I agree. It won’t be hard to get sand into that space, but getting it to stay there will be very hard. A lot of draft and avoiding back draft as suggested above will certainly help. But the surface area of the arms, head, and body relative to the volume of the figure is very large. That situation will favor breakout or sticking of the sand. You might have better luck if after following the draft recommendations and considerable attention to finish, using silicate for a binder. But that is yet another skill set to learn and materials to acquire. Lost wax is not an option, I guess. Denis
I would suggest the same. In my limited experience I reckon a core mould would be easier to manage and give less scope for failure.
A core was the first thing I thought of, unless you can cut and file the shape in afterward. One of the problems with packing sand into a confined space is that the harder you pack it, the more tightly it becomes lodged in and will break right off. Pete
You already have a wax pattern, why not lost wax investment or shell cast it? Might be advisable to make a rubber mold and cast more waxes.......first time success may not be realistic or if you want to make more than one copy. Best, Kelly
Carving wax is not very hard so I would expect the sand is getting caught in the wax surface, assuming you have plenty of draft. Are you trying to make a open mold or are you molding top and bottom so there is a cavity between two layers of sand. If you have successfully made one with lots of filing and sanding I would suggest using it as a pattern for the next go around. The harder cast material may work better in sand than carving wax. You can also paint your pattern then give it a fine sanding to smooth up all rough portions to help the sand release. Also, if you are molding it from both sides in the sand you might relieve the back side of the person shape so the sand thickness in the opening at the front is very thin, with a lot of draft toward the back. That would still look about the same from the front but change the thickness of sand which has to be pulled.
for those of you saying that can not be pulled out of sand because of the size 1) get better sand 2) spend some time working with a better patternmaker 3) seriously Apprentice under a good Molder that design is very very workable , I would not try that pattern. it clearly has Backdraft, and wax ... OK seal it with something to give it a firm surface and wax is workable. I do Not like it in the application he has made, but it is possible . I have many patterns with much more challenging design issues then that I work with all the time V/r HT1 P.S. I'm vaguely interested in how someone would do the Human cutout as a core ... it's beyond Tiny
Wow! Thank you all for the quick responses! Tobho, HT1, David: I think I don't have draft nor do I have backdraft (which is a rounded piece correct?) My edges are more vertical with a very tiny rounding of the edges (or is this what is called backdraft?). I might try a better tapering. Al Puddle: I do not understand what core is, that is something I have yet to learn! Melter, Kelly: I would love to learn lost wax, however my budget is tight at the moment and the sand casting was more economical for all the various pieces I want to make. I knew going in I wouldn't get the detail I see in my head with it but I needed a starting point and felt this would be the best way in. Petee: I'm trying to save myself some time/effort by doing the casting. My hope is/was to be able to cast a decent piece that only needed some sanding/polishing. Oldironfarmer: I am sandwiching the piece between two layers of sand to make the cavity. So what you're saying is to leave a thin layer of pattern in the human shaped void that would create a thin cavity to cut out later, am I understanding you correctly? HT1: What do you mean by "I do not like it in the application he has made" do you mean you don't like the wax as the pattern? I figured it wasn't the best but I wanted something that was easier/forgiving/cheap to make patterns out of as I get my start. Do you know of another option that is relatively cheap but works better as patterns? I would love to get an apprenticeship or to take classes and I'm actively working on finding one in my area that will take me under their wing. As for the sand I don't remember off the top of my head it is red/ochre colored and came with a beginner's sandcasting kit I bought at a local jeweler's supply store. I greatly, greatly appreciate all of your help in educating me with this awesome art form! Here's the piece that came out after I cut out the human form. I'm still in the sanding process and will be engraving it with a design on one side. Ideally I want to make a bunch of patterns in wax, get a decent cast to sand, and then use that as my pattern but I'm not there yet. Thank you again!
Looks good to me and welcome to the forum. Make sure you keep us posted of your future projects, things only get easier....
Looking pretty good! Are those multiple castings or before and after cleanup pictures? My suggestion was to make the final casting thinner near the human form so there's not so much pattern depth to grab the sand. You can take one of those castings or that casting, and grind a taper (draft) undercut toward the back so to sand will part at the front of the pattern. The defects can be filled with wood putty or Bondo and sanded when you make one of these into a pattern. Working with a metal pattern it's easy to grind away and fill with putty then sand away again to get a finished shape you want. We will try to explain things in descriptive terminology instead of foundry terminology, but it's a good thing if you learn terms like "draft" as was described by others in pictures. I laughed at HT-1's suggestion you find someone to apprentice with. We would all love that but hose guys are few and far between.
Wow, I think I missed something here. It looks like you did it. There are many books on casting that would be helpful to you at this stage. One that comes to mind is The Charcoal Foundry by Dave Gingery. I know you're not using charcoal but it is a great introduction to sand casting. Very basic, easy to read, cheap on Kindle or paperback. It will introduce you to the basics of the process and terminology. Welcome. Pete
Looks good! If you take another look the diagrams HT1 and I posted to show what proper draft looks like, then imagine if the taper on the sides of the pattern was angled the wrong direction... There would be no way to pull it out of the sand without breaking the sand away. That is what 'backdraft' means. Jeff
If you decide to file the profile with draft to prepare it for sand casting, being sure that a draft angle has been maintained (it does not have to be a uniform draft angle just a sufficient draft angle) at every part of the vertical surface can be challenging. With the curving face and also, I think, curving back surface, your eye may have trouble seeing draft angle especially in that central cutout area. If I were doing the file work, I think I might drill a hole in a board and insert a thin stiff wire into it orienting the wire accurately vertical. Then you could lay the part on the board and use a little flashlight for better visibility and backlighting and slide the part around to see which drafted surfaces need attention and where a little back draft might have snuck in. The central cutout will need careful attention. On a larger part a small square substitutes for the wire, but backlighting can reveal angle errors easily missed. Tiny areas of poor draft will drive you crazy with repeat failure to draw cleanly. How are you going to pull the pattern? I doubt you will want to drill it for draw spikes. Maybe cyano glue and a match stick or two? Remove the glue with acetone. Denis
I would definitely carve that out of wood, if you intend to make lots of them, cast one, and lovingly file it to get the draft perfect and use the Metal one as the pattern. nothing works better for a sand cast pattern then polished metal... I'm sure someone is going to mention double shrinkage, that is a non issue on ornamental work in most cases well Done Keep at it V/r HT1
The picture is of each side of the piece after a long time spent cutting out the center and sanding. I do want to learn all I can about this art form and need to learn the vocabulary, please just be forgiving with my millions of questions! Thank you for the info! Is there a certain measurement/ratio for how tall the draft needs to be? For example let's say a piece is 5mm wide, would the draft need to be 1mm.... does my question make sense? Does cyano stick to brass?
