Hidden Treasure Box - Inlaid Wood Box With Hidden Compartment

This box has an inlaid wood exterior with a custom mermaid design, padded satin lining, and secret compartment in the bottom that is held closed magnetically and only opens if you know how to do it. I looked at a lot of historical furniture pieces for inspiration - Jefferson boxes, letter boxes, captain's desks and spice cabinets were all often built with very clever hidden compartments. The mechanism I used isn't based on anything historical, but it works well and isn't noticeable if you don't know to look for it.

I lack the time and inclination to become skilled at true marquetry. Anyone who knows anything about early furniture making knows how much time, effort and specialized skill is required. I used the precision of a laser to make up for a lot of that skill and effort. That said, this still isn't a project I would call 'quick and easy.' There is a lot of sanding, drying and finishing time involved.

I chose a mermaid motif for this box. When I was doing the design I just kept coming back to the idea of mermaids. I chose a beach glass green for the lining to keep with the theme.


*Check step 2 for a non-laser alternatives update!*

Step 1: Supplies, Equipment and Safety

Supplies

Wood Veneers - a few square feet
I used Birdseye Maple and Bubinga

1/8 inch plywood - about 5 square feet
This is kind of a specialty product - it's primarily for model airplanes and dollhouses.

1/2 inch diameter dowel - a few inches is enough

Wood Glue
Not a good place to cut costs - cheap glues get brittle and your tiny pieces will chip off.

Sandpaper - 1 sheet each:
220 grit
320 grit
400 grit
600 grit

Woodfiller - light and dark to approximately match your veneers

Tack Cloth

Varnish - water based satin finish is my choice

Clear Contact Paper (clear low tack vinyl)

Rubbing Alcohol

Magnets - two very strong 1/4 magnets

Epoxy - a few drops to glue in the magnets

Metal - 1/2 by 3 or so, has to be magnetic. Soup cans are a good source for this.

Wire nails - a few of them 1/2 long

Satin - about a yard (half a yard would have been enough but it would have been close)

Batting - about a yard

Cardstock - acid free and matched to your satin is best

Thread - to match the satin. Standard sewing thread is fine.

Fabric glue - ideally one that glues fabric to other porous surfaces well

Assorted household type supplies - paper towels, masking tape, scissors, pins, etc.

Tools

Laser access - if you can't find one locally there are quite a few services online that you can find with an internet search. There are some veneer specialists - I didn't use that but it would be worth looking into.

Clamps - all the clamps you can track down in all the sizes you can find (up to about 6 inches of clamping ability.) You'll be using these to hold the veneer as it dries so you'll want a bunch.

Hammer

Needlenose Pliers

Small saw - coping saw or other small, thin hand saw

Tin snips

Utility knife with fresh blades

Small Wood Chisel

Brush for varnish - golden taklon is my first choice because it leaves a smooth finish and is easy to wash out.

Spreader/squeegee/cut cardboard for glue spreading

Letter opener or other dagger shaped non-sharpened instrument

Some scrap flat pieces of wood to protect the veneer when gluing

A few heavy books (Gardner's History of Art works well.)

Safety Gear

Safety Glasses
Dust Mask
Gloves

Use all of these all the time. It's easy to get hurt using tools. If you don't know how to use something find someone who does. Protect your eyes from flying debris, protect your lungs from dust (you don't know what's in the plywood glue or varnish) and keep your hands safe. Sharp tools are always better than dull ones, use the least force required to complete anything.

Step 2: Setting Up Your Files/Non-Laser Alternatives

Lasers like vectors. If you don't know how to design with vectors the internet is full of tutorials on the subject. I used Adobe Illustrator to design my files. I won't go into it too deeply here, but there are a few important things to know.

When you are printing a document you can overlap whatever shapes you want and the one on top prints. When you are using a laser it will cut every single line in your document. Learn to use the "pathfinder" tool panel. Your file needs to be something that will fit together like a puzzle.

Think about the wood grain direction for your pieces. I turned all of the pieces of my compass rose to point the same direction when lasering so that the grain would form a 'starburst pattern.

Have extras of your tiny pieces cut. It's hard to keep all of the small parts together and unbroken. This also gives you options if the grain is inconsistent.

I included a .dxf file and .jpg file of the parts I used. Let me know if you'd like a different file format and I'll try to accommodate!



I had my plywood laser cut because I don't have the tools to cut it as accurately as I'd like. I used interlocking corners because that helped keep the sides square and gave me a large amount of glue surface area. It's good to clean up any dark areas on the plywood with a little rubbing alcohol. The dark areas are carbon and oils from cutting the wood and can make it harder for glue to adhere.


*Non-Laser Alternatives*

I dug through my toolbox and came up with a couple ways to do this if you don't want bother with having parts laser cut.

Alternative 1:

-Plan your veneer panels with minimal curves (the crests work, but anything like the mermaid would be a challenge).

-Print out your design/copy it/whatever and cut it up into pieces.

-Cover your veneer with a low-tack painter's masking tape. This will help stabilize your veneer against the various pressure you'll apply to it. Don't press down on it too much or it will be difficult to remove.

-Trace your pieces onto the tape (keep your grain direction in mind).

-Cut with scissors. Sharp, large, ordinary scissors worked the best for me. 'Cut through a penny' style scissors cut easier but because they are bulkier it's hard to get very sharp curves.

-Cut details with an exacto style knife. Knives are harder on your hands because of the pressure required to use them and tend to get caught in the grain. They are also more dangerous for obvious reasons. Save this for anywhere it's not reasonable to cut with scissors. Keep a lot of fresh blades on hand and change them regularly - you want to cut through the wood, not crush it. My first choice is a high quality snap off style knife. High quality blades last a lot longer than cheap ones do (at least for me) making the initial price worth it in the long run.

-Peel the masking tape off and follow along with the contact paper. Leave the veneer flat and peel the tape when you remove it.

Alternative 2:

I tried a jeweler's saw and was able to cut the veneer very smoothly with that. Use a fine blade and let it cut - don't put any unnecessary pressure on it to avoid breaking the veneer. This will give you more detailed curves than the other alternative, but it takes a lot longer and I would guess most people don't keep a jeweler's saw around. A coping saw might work as well but I'd use the smallest available blade.

Step 3: Assemble the Box (Part 1)

The box has two layers - an outer layer that the veneer attaches to and an inner layer to keep the lid aligned and hold the hidden compartment.

Sand all box parts with the 220 and 320 sand paper until they are nice and smooth. This is to avoid having to sand so much inside boxes later.

Assemble the boxes by applying glue to the edges and pushing them together. Always dry fit your parts before gluing to double check the fit. Use clamps and masking tape the hold parts together while drying.

Glue up the outer lid, inner lid, and outer lower box (separately.) Allow to dry.

The inner lower box requires a miter cut in the top 3/4 inch or so into both sides of each panel. This allows the inner box that shows to have nice clean mitered corners. On two panels its the top tooth that needs to be mitered, on the other two panels miter down to the small 1/8 horizontal cut. Use the coping/hand saw to do this, or use the utility knife if you need to. Dry fit, and once the corners are nice and sharp glue it together. You can fill in any gaps with the light colored wood filler (sand smooth when dry).

Miter one side of the outer side of the bottom door panel at 45 degrees. This will allow it to swing smoothly and be the indicator of where to push to open this compartment. Sand it nice and smooth. Glue the hinge parts together and glue them to the inside of the bottom door panel at the mitered edge.

Make sure the outer box top fits over the lower inner box smoothly. Sand both parts until the top slides on and off easily and smoothly.

Glue the hidden compartment sides into the bottom of the outer lower box (making sure the prop them up the 1/8 inch to allow for the bottom door to close.)

Double check that the magnets fit into the strip, adjust if necessary (a rotary tool is handy for this.) Remove the magnets. Glue the strip that holds the magnets to the inner side of the bottom door, set back 1/8 of an inch from the edge.

Glue the magnets into the strip with epoxy. Use epoxy because it's easy for a strong magnet to hold to metal more tightly than the glue holds to the magnet, effectively ripping the magnet out of it's glue base. Epoxy improves the odds that this won't happen.

Step 4: Varnishing

Any time I say to varnish a part, these are the steps to take:

*Always sand and varnish in the same direction as the wood grain. In case of multiple grain directions majority rules.*

Sand the piece with 220, 320 and 400, making sure it's smooth an even after each level.

Get the area lightly damp with a wet paper towel. Allow to dry. This raises the grain a bit. Once dry, re-sand with the 400 grit paper (320 if the piece became very rough, then 400.)

Wipe over the surface with the tack cloth to remove any wayward sawdust.

Apply a smooth, thin, even coat of varnish. Allow to dry completely.

Sand lightly with the 400 and 600 grit sandpaper.

Wipe with the tack cloth.

Apply another thin coat of varnish and allow to dry.

You can repeat the sand/varnish cycle as many times as you want. My box has 3 coats.

Step 5: Box Assembly (Part 2)

Use the varnish instructions to varnish the inner part of the outer lid (only where it will be exposed) and the outer part of the lower inner box (again, only where it will be exposed.) Make sure these parts still fit together. If not, sand to fit and repeat the finishing.

Check that he inner box top fits into the outer box top. Sand if necessary. Glue in place with wood glue.

Step 6: Assembling Veneers

This is the puzzle part of the challenge - allow some undivided time for this. Honestly, I was disappointed by how quickly I was done with this part. I would make a million of these.

Print out the pattern (especially for the top.)

Cut a piece of clear contact paper an inch or two larger than the veneer section.

Removing the backing. Tape it sticky side up on top of the pattern.

Start placing your veneer pieces, nice side down, on the pattern. Work from the center out. If you set them down lightly that will give you a lot of nudging room to get them exactly how you want them. Dont push the pieces too close together if you can avoided it because they expand just a bit temporarily when you glue them and this can prevent it the pieces from laying flat. When youre done lay the backing piece over it again and stick it around the edges to keep the veneer clean. Assemble them all. Stack them in a safe, flat, dry place.

Step 7: Gluing Veneers to the Box

Make sure the plywood is sanded smooth. Fill in any voids with wood filler, let dry and sand down flush. Wipe the surface with the tack cloth.

Set the veneer piece on the box where it will be glued. Check the placement, figure out how you want it, make any adjustments to the veneer that you need to. Youll need to place it quickly when the glue is on the box so take your time now.

Use the squeegee/cardboard strip to spread a nice, thin, even coat of wood glue over the entire are of one panel of the box. Use just enough to cover, too much will ooze out an make a mess, too little and the veneers wont stick. Youll be able to tell when youre working with it what kind of glue coat you need.

Place the veneer piece on the box. Adjust it as necessary to place it exactly. Put a scrap board over it and clamp it tightly in place. Use as many clamps as you can fit. For the top I set the lid on top of a spool of blank CDs and stacked heavy books on top of the box instead of clamping because I couldnt get a good angle for my clamps. This resulted in slightly more texture than just clamping but it still sanded smooth.

Allow to dry (overnight is best.) Unclamp. Leave the vinyl in place to keep the panel clean and glue free.

Repeat on all of the other pieces. Its a good idea to have the inner lower box slid into the outer lower box for sturdiness when you do those panels.

When all of the veneers are glued in place carefully peel back the vinyl. You may need to remove some adhesive from the box - use rubbing alcohol for that. Fill in any gaps with the wood filler - dark in the dark areas (like the corners), light everywhere else. Allow it to dry very well, then sand it smooth. Follow the varnishing directions to apply finish to all of the box.

Step 8: Box Assembly (Part 3)

Mark on the metal catch side where the magnets are. Cut a piece of metal with your tin snips to fit that area. Use the chisel to carve down a depression deep enough for the metal to sit in it and be flush with the rest of the piece. Use a couple of wire nails to hold the metal in place, bending over the extra nail on the back of the piece. This will keep it from pulling away and attaching to the strong magnets.

Glue the metal catch pieces into the bottom of the box.

Step 9: Lining

Print out the box lining panels on the scrapbooking paper (or transfer the measurements to the paper.) Glue pieces together with strips of paper if you need to.

Cut batting pieces a bit larger than the cardstock pieces.

Cut satin pieces a couple inches larger than the cardstock pieces.

Use a straight pin to put a hole in the center of each circle on the pattern.

Thread your needle, tie the two ends together with a substantial knot.

Stack the batting on top of the cardstock, the satin on top of that. Start at the center. Sew up through the hole you punched, through all of the layers, then back down through the layers and hole, leaving a very small stitch on the satin side. Pull it down to leave a depression on the satin side. Stitch up through a nearby hole and repeat. I spiral from the center out to keep the fabric even and smooth. Tie off your thread at the end (or part way through if you run out. Just re-thread and keep going.)

After all panels are sewn trim any extra batting down to the edges of the cardstock. Test fit the pieces in the box parts.

Trim down the satin to an even margin - about 1/2 past the edges of the cardstock. Leave the satin in what will be the corners of the box. Use the fabric glue to glue the fabric back over the edges of the cardboard. Allow to dry.

Step 10: Box Assembly (Part 4)

Sand and finish the outsides of all box pieces, following my earlier varnishing directions. Put a coat of varnish everywhere that lining will be glued - no need to sand this, though, the texture will help the glue adhere.

Glue the lining piece to the inside of the bottom compartment door. Glue the compartment lining to the panel that separates the top and bottom compartments. Use the fabric glue and clamp where necessary. Allow to dry.

Using the small hand saw cut 2 dowel pieces the same length as the hole through the hinge pieces - about 3/8. Sand until very smooth.

Set the lower outer box over the bottom door. Put glue on one end of a dowel piece. Slide it through the hinge and glue it to the box side. Be careful not to get any glue on the hinge. Repeat on the other side. Allow to dry.

Glue the metal catch strip to the other two pieces, glue into place.

Apply glue to the unglued lining parts on the separation panel. Drop into place. Flip over the box and push the lining against the sides of the compartment. Allow to dry.

Glue the lining into the lid of the box. Use the letter opener to tuck the corner fabric behind the lining cardstock and out of the way. Be sure its glued securely.

Glue the inner lower box into the outer lower box with wood glue. Glue the lining inside of that. Glue the lining to the inside of the lid.

Step 11: Conclusion

To open the secret compartment apply pressure at the beveled edge above the hinge. This will make the magnet release and pop it open.

The veneers are pretty fantastic to work with. They're about the thickness of cardstock and cheap - these were around $1 per square foot and the cardstock was $.60. It's a nice way to use exotic materials in a responsible way. You can get thousands of square feet of veneer from one tree and then glue it to something that is more easily and efficiently created. This was my first time doing anything like this and now I'm completely hooked - both on the materials and engineering secret compartments.