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Uploaded 10|12|2002 - Updated 11|19|2002

Earth><Mars><Moon "Gravity Bricks"

A full set of instructions for making your own set
using common bricks, 3/4" styrofoam, etc.

by Peter Kokh, Lunar Reclamation Society (NSS-Milwaukee)
Wisconsin Mars Society, Moon Society Milwaukee Outpost

Photo of a completed Set of Gravity Bricks
L>R Earth, Moon, Mars

You can order a set pre-made for $15 per set plus USPS shipping (from Milwaukee, c. $10 +/-) Payable to Peter Kokh - Allow 2-3 weeks lead time before your must-have-by date. Maximum production 6 sets per month. Excess orders not accepted.

The aim of posting these instructions, however, is to encourage others to take up this "craft" and thereby lesson the growing demand on the original supplier.







(4) common bricks or pavers - bricks with holes in them make handle attachment easier. The bricks I have been using are 3 1/4" wide, 2 1/4" high, and 8" long. These proportions work well.

Liquid Nails Heavy Duty (1 tube) - if you choose some other brand, make sure that it is safe to use with foam board. Many brands (and other kinds of Liquid Nails) will eat away the foam board

(1) sheet of 3/4" styrofoam (easy to find 14.5" wide in 4' and 8' lengths - you can use the remainder of the sheet for protective packaging

(3) 6" lengths of pre-bent gray plastic conduit [1/2" 45° "sweeps"] from the electrical supplies bins of your local home center or hardware store - they are of minimal weight (that's important) and will be your handles, allowing visitors to pick up the bricks. If you can't find these (57¢ apiece at my source) buy a straight length (you'll need about 18-20 inches) and cut it into short lengths. Any black writing imprinted on the side wipes off easy with a little acetone.

(4-5 ft) plastic sheathed 14 gauge solid wire - you can buy this by the foot in the conduit wire area of electrical supplies section of your home center or hardware store (or pull either the white or black coated wire out of a length of Romex) - this wire is threaded thru the plastic bends and attached to the bricks

either bathtub caulk in a squeeze tube (do not use pure silicone!) or sprakle (to fill any gaps and disguise the seams of the layers of styrofoam (5) you will use on the exterior of your Moon and Mars bricks

Optional: any leftover scraps of 1/8" or 3/16" wood ply paneling you may have laying around (thin is good enough, and you don't want to add too much weight) - the idea is to use these pieces to protect the sides of your Moon and Mars bricks from handling (pinching) damage by over-curious visitors who somehow imagine that they actually came from the Moon or Mars!

Latex primer (oil-based would eat into the styrofoam)

Optional Base coat to give underlying color: I use a gray latex for the Moon brick, a terra cotta shade latex for the Mars brick. ( I didn't have either, whipped them up by mixing colors I did have on hand.) Another advantage of this step is that if you just use a white primer, you may not notice that you have skipped spots on the white styrofoam. And that will lead to the problem described in the "caveat" just below.

(2) cans of Zynolyte Fleck-it Spray or Krylon Make-It-Stone Spray - 1 can in gray shades for the Moon brick - 1 can in sand | rust shades for the Mars brick (and, optionally, the assembled Earth brick). It is the multicolor flecks that help create the illusion that these are "bricks." CAVEAT: resist the temptation to skip the primer as the Fleck spray will seriously corrode the styrofoam surfaces of your Moon and Mars bricks if you haven't latex-primed them first. SOURCES: I have had better luck finding these specialty spray paints in Ace Hardware stores than in the big chain Home Centers. Price per can is in the $7-10 range, but the effect is worth it.

Acrylic flyer holder: (Clear Frame 8x10 Photo Holder) you want people approaching your table to get an idea of what this is all about, and a bit of text lying flat on the table top just doesn't quite do it.

NOTE: Cost of supplies. You will find your supplies will cost you more than the $15 charged per ordered set. That is because I have had access to a free supply of bricks, and have been averaging the cost of paint, drill bits, and other items over several sets.



Option A - Wet Saw (the route I took) A wet saw with a diamond blade is a device for cutting ceramic tile, marble, patio blocks, bricks etc. - You can rent these from your tile store. These are big, heavy, cumbersome. I happened to have purchased a small table top wet saw for my home improvement day job in 1996, and indeed it was the fact that I had this ideal tool that led to the idea of the "Gravity Bricks" in the first place (in 1998). For about twice the price of a typical wet saw rental, you can buy a small one that will do very well, and afterwards you will have just the tool you need to do expert ceramic tile floor installations and other jobs around the house. Mine [manufacturer's photo] is manufactured by Plasplugs, and it is still available at Menards (Midwest states home center chain) for $99. The Plasplug website seems to have a lot of not-yet-activated links, and I could find no list of distributors, or a U.S. phone number. The set is manufactured in Britain.

Option B - Circular Saw with Masonry Cutoff blade - I didn't try this, but it should work. The cutoff blade will wear away rapidly, but one might do the job for the 4 cuts needed.

Electric Drill with 3/16" carbide tip masonry bit - to drill holes for the attachment of the handles. Forget what you've heard about DeWALT. I tried two of their bits and they both wore out before I finished one hole. I much prefer the Vermont American brand, and get several holes out of each bit.

Caulk Gun to use with caulk tube of Heavy Duty Liquid Nails

Putty knife or small scraper - comes in handy to take care of liquid nails splashout and to blend in the seams between layers of styrofoam

Table saw - sorry to say, but I can't imagine any other way to cut the styrofoam accurately and without a lot of hanging stryrofoam beads. You will also need the table saw to cut sections of 1/8" thick wood ply paneling scraps. Chances are that if you don't have a table saw, a circular saw, and an electric drill, this project will prove to be too ambitious for you. But their are options.

Serrated steak knife - to cut out the cavities in the styrofoam that will hold the actual brick components (Moon and Mars Bricks)

Everyday Steam Iron - set on high, no steam - useful in evening out the edges of the styrofoam layers and in rounding their corners - practice first! Just a light touch will do!

some kind of hooks to suspend your bricks after painting while they dry (8-12 hours) - I hang mine from the cross braces of my basement ceiling joists.



STEP BY STEP INSTRUCTIONS: NOTE: I have been making these brick sets for over 4 years (since February 1998) and have made several simplifying improvements to the process. The instructions below reflect how I am making these sets as of October 2002 ("Version 4.0"). I have chosen to forgo any method and step simplifications that might compromise the effectiveness of the visual and tactile illusion that is involved in creating the sudden rush of insight the visitor gets when picking up the bricks. - Peter Kokh

Step 1. Cutting the Bricks:
(A) Earth Brick components: lay two bricks on their long edges side by side. Take a third brick and cut off a section (about 5/8ths of its length) equal in length to the double brick's width. You will cement the two bricks together with Liquid Nails, and put cement the cut off section to one end. This will form the Earth Brick. All you have left to do is add the handle (and, if you want, disguise the seams by filling them in and spraying the whole assembly with a fleck paint)

HINT 1: The bricks I have been using are 3 1/4" wide, 2 1/4" high, and 8" long. These proportions work well. Proportionately thinner bricks would result in an Earth brick that was a bit lighter than ideal, and a Moon brick that was a bit heavier than ideal.

HINT 2: depending on the cutting depth of the saw you use, you may need to make two cuts, one on one side, then flip the piece over and make a cut on the other side. If there is still a "bridge" of material left, this is no problem. Simply stick the head of a chisel or flat screwdriver into the cut and tap lightly and the two parts will split. I do not bother to smooth out the bridge remnants that remain.

(B) Mars Brick - one whole brick, no cutting needed

(C) Moon Brick - take the remnant left from the first cut and cut that in half along either of the two longer dimensions (about the same). These two pieces will supply most of the mass for your Moon Brick. Cutting hint: see HINT 2 below Earth brick illustration above.

Step 2. Cutting the Styrofoam Pieces:

The idea is to come as close as you can to the dimensions of the Earth brick. Five layers of 3/4" foam board will come close enough. You have to cut them in slabs that are the same width and length as the assembled Earth Brick. Set your table saw fence so that your Earth Brick just fits between the saw and the fence. Rip enough styrofoam to get 2x5=10 lengths (the length of your assembled Earth Brick) out of it. Reset your fence and use your sliding miter guide to pass the foam strips thru the saw and cut them to the desired length.

Step 3. (Optional) Cutting the plywood paneling scraps

The idea is to produce protective side panels for your bricks. Once primed, base-coated and sprayed with fleck paint, no one will notice that they are wood if you have done a good job of blending in the edges where they abut the styrofoam. Stack 5 of your precut styrofoam slabs together. You want your panel strips to be just slightly less wide than your stack is tall, just slightly less long than your stack is long. This will make blending easier. Note that the use of protective panel strip sides greatly lessons the job of disguising the but joints between the styrofoam slabs - you'll have just the two ends to worry about.

Step 4. Making the Handle Assemblies

Cut three 18" lengths of the 14 gauge plastic-sheathed solid conduit wire

Bend each length in half. Put the bend in a bench vise and, grabbing the two ends, tie a loose knot about 3/4" across in the center of the wire length

Thread one end of the wire through the gray plastic conduit piece, using a pliers to squeeze the knot so that you can just pull it through (into the middle of the conduit section) with steady force. The idea of the knot is to provide just enough friction on the inner wall of the conduit section so that that the conduit handle does not slip back and forth along the length of the wire.

Step 5. Securing the Handles to the (real) brick components

Using your electric drill and a 3/16" carbide tip masonry bit, drill holes into the Earth brick assembly, the full brick you will use for the Mars brick assembly, and the two remnant brick pieced you will use for the Moon brick assembly. Drill into the hole free side of the brick above a hole. Your holes should be 6-7" apart ideally, and try to make them equally off center at both ends of the brick assembly, so that when the assembled brick is picked up, it is acceptably balanced.

Now thread the handle wire through the drill hole, into the brick hole, grabbing it with a needle nose pliers. Once you've pulled through enough wire to work with, bend about 3/8" of the wire back on itself, and secure the doubled section with a thin strip of duct tape. This makes the end to big to be pulled back through the drill hole when the bricks are picked up by visitors. Pull the excess wire back up through the drill hole. Repeat with the wire on the other side of the handle.


Step 6. Assembling the Mars Brick & Moon Brick

The mass of the Mars brick assembly rests in the one intact uncut brick. You will create a pocket through all 5 styrofoam slabs to hold the brick on its narrow side, per the illustration below, trying to line up the pocket holes as precisely as you can so to avoid adjustments later. Test fit the five slabs with the clay brick to see if you need to play with the pockets to improve overall alignment.


The mass of the Moon brick assembly rests in the two smaller brick pieces cut from the remnant - see illustration for step 1 above. You will create two pockets through all 5 styrofoam slabs, as in the illustration above, trying to line up the pocket holes as precisely as you can so to avoid adjustments later.

HINT: place the brick piece(s) on the uncut slab, measure to be sure you have it (them) centered, score around the brick piece(s) with your serrated stake knife, then set the brick to the side and slice through the foam carefully, trying to keep your knife straight. Test fit the brick, but do not force. If it does not want to friction fit easily, remove material from the side of the pocket hole (one or more pocket hole walls may slope inward or outward if you didn't succeed in holding the knife straight, as I usually don't). Remember, do not force the fit as you will break the fragile foam slab at one of the pocket hole corners. Then repeat with each slab, transferring the alignment location measurements you used to locate the pocket in the first slab. Taking care to do this patiently, will result in a slab stack that is well-aligned.

Now, for each assembly, take the bottom slab, lay a bead of Liquid Nails Heavy duty along the top, with a few dabs on the top inside edges of the hole cut for the clay brick.

Slip in the clay brick piece(s) (handles already attached)

Next position the next slab on top of the first. Butter this slab with Liquid Nails and place the next slab on top of it, sliding it over the clay brick piece(s). Be sure to put some dabs of Liquid Nails along the interface of each slab and the clay brick.

Making sure that the slabs are aligned as well as possible, especially along the long sides, butter the two paneling pieces and attach one to each side, again lining up the panel strips as well as you can. Adjustments are much easier when the Liquid Nails is fresh than after it has set.

Now your Moon Brick and Mars Brick Assemblies are nearly ready for painting - but not before the Liwuid Nails is firmly set (allow 8 hrs minimum or wait until the next day)


Step 7. Touching up the alignment - filling & smoothing the joints

The next day, examine each brick for slab alignment on the exposed ends. Protruding slabs can be compressed into alignment with a gentle touch of a hot steam iron (steam off). Experiment with foam scraps first! Similarly, you can use your iron to gently round exposed corners, etc.

Next you want to fill any noticeable gaps - between the slabs, between the foam pocket hole and the brick piece(s), between the slab stack and the protective side panel pieces. You can use bathtub caulk or sprakle for this job, gently smoothing with your finger.

HINT: if a protective side panel sticks up above or below the foam slab stack, and you have used a thin all wood paneling scrap to make the panels, you can easily shave the excess with a utility knife. You can also use the utility knife to put a chamfer on the edges and corners of the panels - after all, bricks don't usually have "sharp" edges and corners!

Finally, remember, bricks are supposed to have irregularities! You don't need, or want, perfection!

Now when this caulk or sprakle has dried, you are at last ready to prime.


Step 8. Priming, Base Coating, Finish Coating the Moon and Mars Bricks

After the Moon and Mars brick assemblies have dried (allow 8 hours to be sure), pick up each assembly, grabbing the center top with your holding hand under the handle, turn the assembly so that the bottom is facing you and prime the bottom. Then turn the assembly to paint successively the ends, and as much of the sides as you can without getting paint on the hand you are holding the assembly with. Then, brush down, use your working hand to grab the assembly by the handle, and transfer this grip to your holding hand. Now you can prime the rest of the two sides, and the top. Hang the assembly by the handle on a suspended hook (now is not the time to look for one!) to dry.

When the primer is fully dry, you can apply the optional (but advised) gray base coat to the Moon brick assembly, and an ocher or rust coat to the Mars brick. For this you can use latex paint if you have it, or gray and rust spray primers (once the assemblies have been primed - if you skip the priming step, the spray primers will eat into the styrofoam severely).

When the optional recommended base coat is dry, similarly holding the assembly with one hand, apply the Zynolyte Fleck-it™ or Krylon Make-It-Stone™ spray. Allow this to dry thoroughly (overnight is good) before handling the brick assemblies directly (as opposed to by the handle.)

You may apply a spray clear coat if you want - I have never done this and it doesn't seem necessary, except to provide the manufacturer with more income.

Step 9. The Accompanying Flyer Stand (Clear Frame 8x10 Photo Holder) - [illustration]

Ready-to-go explanatory flyers with blank boxes at the bottom for your group name and contact information.

BrickFlyerBW.pdf - a black & white version

BrickFlyerC.pdf - a version with color depictions of Earth, Moon, Mars

NOTE: These acrylic flyer stands or Clear Frame 8x10 Photo Holders will not take a full 8.5x11 sheet, so you will have to trim the margins of your printout.

Step 10. Storage and Transport

A 10 ream paper box will do nicely, with enough room for padding using styrofoam scraps. This is ideal for shipping your set by USPS (cheapest), UPS, or FedEx to a convention or other out-of-area display event. A smaller box will do for local use, if you skip the padding.




But you have NO WET SAW
and no circular saw with masonry cutoff blade

Check out our "Gravity Jugs"
Make your set in less than 1 hour for less than $5"

But if you still want "bricks" (they'll do a better job in attracting the curious to your table,) read on

  • Earth Moon 2 brick set - mass ratio 6:1
    • 6 bricks (c. 21 lbs.) to 1 brick (c.3.5 lbs) jacketed to be the same size as the Earth 6-pack
    • Or find some unit less heavy than a common brick
  • Earth Mars 2 brick set - mass ratio 8:3
    • 8 bricks (c. 28 lbs) to 3 bricks (c. 10.5 lbs) jacketed to be the same size as the Mars brick 8-pack
    • Or find some unit less heavy than a common brick
  • Mars Moon 2 brick set - mass ratio 8:3+
    • The same set that you use to demonstrate the difference between Earth gravity and Mars gravity will come close to giving you the feel of the difference between Mars Gravity and Moon gravity. But the set would not allow you to compare Earth gravity to Moon gravity
  • An Earth-Mars-Moon gravity 3 brick set - mass ratio 24:9:4
    • using uncut integral elements, would require 24 mass units to represent Earth, 9 mass units to represent Mars, 4 mass units to represent the Moon. If you use common bricks you would have a very unwieldy set weighing 84 lbs, 31.5 lbs, and 14 lbs respectively. Obviously, you want to look for some unit that weighs much less than a brick, but which you can combine as blocks.
    • Wood has the attraction of being much easier to cut, but its lower density (about a third of brick) means you may end up with "bricks" that are of a convenient weight range, but very bulky in size.
    • Water filled containers would also be much less dense than brick - but if you want to go that route, check out our page on "Gravity Jugs."
    • Sand | aquarium gravel | marble chip | cement filled containers of a convenient size might work well. (Something like sugar would be too light.) You'll find it easier to work with containers that stack or gang together neatly, with flat sizes.
      • Perhaps those tins of international flavor coffees, even though they have round corners, ganging them top to bottom just might work.
      • Similar but smaller are sardine cans. Fill them with cement, and after drying, duck tape them together top to bottom to make your 24 unit Earth brick (2 rows of 12), then prime, base coat, and fleck spray. Handles? You will figure it out something.

        ILLUSTRATION to be added

      • Safety Match Boxes filled with sand (or one of the other fillers mentioned) is another idea
      • Let us know what you come up with.