[rbrittigan]

Ok, folks -> first tutorial, so be gentle. 😊

Ok, to be clear -> these are intended to last a very long time, but to really be seen at a distance. While some will come out quite nice (they go up front), most will have anomalies; which I find kinda cool. I use them primarily as fillers, but you can carve them, and they hold most paints well.

Materials needed:
Mold -> here I used ShapCrete, which I was able to snag for cheap; it hardens to almost concrete like strength, but weighs a little less. Easy to work with, but it’ll take some patience. I think it ran me $12 per bucket, one bucket was enough to build 2 molds, 21” high each. (that was on clearance, btw.) It’s a permanent mold, almost infinite uses. I think you could likely also use wood or melamine, since I also use plastic wrap to keep things from sticking.

Sika PostFix -> ok, I know I could get the two part resin expanding foam in larger quantities, but it’s expensive. Turns out the Sika PostFix bags (pictured below) contain both Part A & Part B; and the ratio is a 1 to 1. So I cut the bag along the middle of the break line, then pour the material into their own containers (dollar store, also pictured). Each side contains ~16 ounces; you will need ~10 ounces of each part for 1 tombstone (my size, anyways). Two bags effectively nets 3 stones. They run ~$12 per bag. I recommend gloves and glasses, and heck, an apron. This stuff will stick, kinda like Great Stuff. Be aware it’s an exothermic reaction, so it gets a bit warm.

Plastic Wrap -> I use the pallet shrink wrap stuff, mainly because I was able to get some for free. It’s only to keep it from sticking to the mold; if you use melamine and/or the PVC sheets (the plastic white ones) it may not be needed. Be aware, folds in your plastic will result in ridges in your tombstones.

3 medium / large plastic containers -> I got mine from the dollar store. Pictured below. While you are there, pickup the cheapie plastic measuring cups (also pictured). They are cheap, and the individual parts don’t stick to the cups. The cured portion doesn’t stick to the large containers, either, and they are just flexible enough to pull the remnants out and get clean enough for the next batch. (You’ll understand after the first batch)

½” PVC -> I cut mine into ~10” segments; these are stabilizers, the part I drop onto tent nails to hold them in the ground. (See image below in the build part). I think they just work better that sticking the stake directly into the stone.
Bird Netting or hardware cloth -> Ok, this may be overkill, but I am kinda weird that way. I use these between the two 10” PVC segments (as noted in the picture) to add structure / strength. Likely not needed, but…
Paint as desired, possible moss and other touch ups.


Build:
Get your molds built. Since this has many solutions, I didn’t bother walking down that path with what I did, outside of taking measurements from real stones & duplicating. If you use ShapeCrete, be aware it’ll need to cure, so add ~48 hours into your beginning steps.


Once you have the mold built, I highly recommend you stage everything before you combine part A & B; you have roughly 15-20 seconds before the show starts once you mix the two, and you really want to let it expand unhindered unless you like the lump design (as pictured later) so be ready.
Pour ~10-12 ounces of each part of Sika into a separate measuring cup; depending on the size of your tombstone (mine is 21” tall, I use about 11 ounces of each part, so…).
Cover your mold with plastic wrap; be sure it’s all covered, and don’t re-use. If you have a hole or miss the sides it will stick. You have been warned….
Place PVC rods and netting (if used) into mold (as pictured below):

Ok, showtime; pour both Part A and Part B into your ‘mix’ container (as pictured). Shake vigorously for ~15 seconds, then pour onto mold. A few notes here -> it’ll look like a tiny amount -> it’s not. Be sure to cover the edges, then backfill around the pvc -> meaning a large portion in the middle and along the pvc. It’ll grow (also as pictured). Once again, it’s exothermic; you have been warned.

~30 seconds ~60 seconds
Ok, after about 30-45 seconds you will see it start to grow a fair amount. Once it’s above the PVC or if it doesn’t quite make it to that you can ‘jiggle’ the mold for better spread; if you choose to guide (with latex or nitrile gloves) it’ll turn out lumpy (and be very warm). That’s ok, you can see the comparison images below; but you only have ~3-5 minutes to play with it; otherwise it’ll go to set mode.
It’ll cure to a weird green color, light on the exposed side, a little darker on the plastic side. Both will accept paint, so no worries (as a matter of fact the green acts as a nice under color). It’ll take about an hour or so before you can lift it out of the mold and pull the plastic; give it at least another hour after that to paint. Carve as you see fit…

(lumpy on left due to ‘rubbing / adjusting’ during cure; right was left alone -> both sprayed with black cheapie rattle can. One on right looks mottled due to lighting)

Clean out the holes to expose the pvc mounts, paint / decorate as desired. Feel free to place 3-d angels, crosses or whatever in the curing phase and play with it. When I display in the yard I sink 10-12” tent nails into the ground, leaving ~4” above ground; then slide these on. Never had an issue with them blowing over or ‘leaving’ (unless kids snagged them, but that’s another story).
So, in a nutshell; once you have your mold(s) made, you can create a new tombstone per mold in about 2 hours. I do two at a time, and can make 6 in a day (with libation breaks). Could push to 8 or 10 in one day, but did I mention libations? At the end of the day each stone will cost about $8, but will last a really long time. (mine are 5+ years, no sign of issues yet)
Good luck & happy Haunting!

 

[Nightbird]

Where did you find the shapecrete? Everywhere I’m looking states that it has been discontinued.

 

[rbrittigan]

Where did you find the shapecrete? Everywhere I’m looking states that it has been discontinued.

Home Depot; I stocked up while it was on clearance. Now I guess I know why it was on clearance
You can try the melamine or coro plastic; key is to frame it solid, but you might still have to cover in plastic. I use the PVC sheets for resin pours, that may work as well (but is kinda pricey). (I plan on using my last batch of shapecrete for one of those empty cloth figures sitting on a bench...)

 

[rbrittigan]

Where did you find the shapecrete? Everywhere I’m looking states that it has been discontinued.

Also, I found this:

sculpting - Alternative to Shapecrete - moldable concrete that is workable like clay - Arts & Crafts Stack Exchange

 

[Cranium]

View attachment 748722

Do you consider this the front? Do you have a pic of how the other sidelooks.

 

[rbrittigan]

Do you consider this the front? Do you have a pic of how the other sidelooks.

Those would be the front; turns out it goes better with ~12 ounces of each part, covers the lines from the PVC. This is what the back typically looks like...

Remember; paint, lighting and distance are your friends here; once painted you really see the textures as natural stone.

 

[rbrittigan]

Those would be the front; turns out it goes better with ~12 ounces of each part, covers the lines from the PVC. This is what the back typically looks like...

View attachment 748788
Remember; paint, lighting and distance are your friends here; once painted you really see the textures as natural stone.

The fold lines you see are from the shrink wrap; I am testing PVC boards now to see if the Sika sticks to them, and what it does to the texture... But even without paint, kinda cool...

 

[rbrittigan]

The fold lines you see are from the shrink wrap; I am testing PVC boards now to see if the Sika sticks to them, and what it does to the texture... But even without paint, kinda cool...

Ok, just to update folks -> Parchment paper is your friend! That's the winner, the Sika will not stick to the shiny side. Problem is getting it in widths of 24" on a roll to fit in my current concrete tombstone molds. I'll be trying some butcher paper this weekend to see how that works; if it works well it kind of opens up a bunch of doors on molding processes since I can build forms with wood, wrap in paper and let it flow.
As a side note, the Sika cures faster and the side on the parchment paper cures the same as the top side, making for flat surfaces to do your carving on!
Pics to follow once I play this weekend...

 

[rbrittigan]

Ok, another 10 stones in; here are some additional observations (apologies for the nerdiness / details);
So I originally stated 3 stones per bag; I am going to revise that to 2 per bag. This is based on increasing to 12 ounces each of part 'A' and part 'B' per 2 tombstones. (originally I had stated 10 oz per part per tombstone, that *should have been for 2 tombstones), That seems to give me the best thickness throughout, especially if you go with the butcher paper. You will have a little leftover and that's ok as long as you store it in the dollar store containers. (unmixed -> the leftovers in your mixed container are toast, but easy to pull out after cured). Make sure you outline the stone with the pour to start, then go to center; and until it sets, swirl it around for coverage. Be aware you have less than 30 seconds after you mix & pour...

Butcher paper -> ok, was originally happy with the test sample; which was originally reinforced with the initial 10 oz mix (10 oz part 'A', 10 oz part 'B').

Then it cured. Which is to say while the paper pulled off cleanly, the stones were thin, and a little soft. Upping that to 12 ounces fixed everything except I could no longer pull the butcher paper off and I thought this was a bad thing, but....

Ok; leaving the paper on 1 side meant I could spray both sides and see what happens; Black Matt rattle cans (cheapie, Lowes) and holy cow these are perfect for me! Just enough character for stones, and seem to give enough depth. I will update after the first rain to ensure the paint doesn't just wash off, but wow! Backside was similar to what I have for the other stones, meaning they would look good in the background as filler. But the butcher paper side.... It's awesome!
Ok, this might be a little twisted, but... With the butcher paper still on, and a light(ish) coating of black matt spray it kinda looks like skin, lightly charred. Which actually makes for a very interesting tombstone; charred flesh wrapped. Is that wrong?

Now on these pictured below I did not use the PVC mount pipes & netting; but I am thinking they will still be ok because they are so strong. On the thickness image 10 oz on left, 12 on right with paper.

The actual stone pictured is with the butcher paper on; I'll let you know if the paint holds.

 

[Engineerchic]

I like this technique ... I might try this with foam in a can, like the Loctite stuff. Have you tried any of the mold release agents (like wax) between your mold and the foam? But I guess that might affect paint adhesion later.

 

[rbrittigan]

I like this technique ... I might try this with foam in a can, like the Loctite stuff. Have you tried any of the mold release agents (like wax) between your mold and the foam? But I guess that might affect paint adhesion later.

Didn't try any release agents, was originally hoping it wouldn't be needed, But still liking the effect once the paint went on! I don't have them out in the yard just yet (slacker, I know) but it will be interesting to see what the weather does to them post paint. I'll throw one in the back yard just to see what it does...