Introduction: Cardboard Pen
There are a couple of people who have tried to do what I wanted to do and wrote their experiences on various blogs. Everybody seemed to have the same issue, getting the cardboard flutes to completely fill. Removing the air seemed like a very simple solution to this problem.
Before I go any further, I just want people to know that this project wasn’t as simple as I had thought. It’s ridiculously challenging! You should expect failures. Read on to learn how to minimize the failures but I make no promises. I wanted to make pens for the office and walked away with a 25% success rate which is only because I shifted a few bits around enough to get additional blanks out of them.
(This blog originally appeared here)
Step 1: Step 1: Build Your Forms
I am using slimline pens which require a 5/8” x 5/8” x 5” pen blank. I already had scraps of ¼” plywood which was cut into strips that were 1.5” wide meaning my blanks would be around 1” square, a little big but that’s ok. I wanted to put the cardboard at an angle so I opted for a 6.5” length. Make certain to assemble your molds to give you a little extra room on top of the corrugated. This space will be needed when you start to vacuum all the air out of the corrugation. I used hot glue to build the forms because I could be certain that all the gaps would be filled and it costs less than caulk. It was a calculated risk to use because of the heat that is created by the curing epoxy.
Step 2: Step 2: Cut Your Corrugated and Fill Your Molds
I scrounged through the recycle bin where the scraps from our CAD
table end up to find something quick and easy to work with. Luckily, there was a nice long strip of B/C double-wall that was already cut into a 1.5” width which was perfect! (If you’re looking to do this project I suggest a triple-wall board which I’ll explain about later.) All that was left to do was to cut 1” strips. I used a paper cutter and fed the strips in backwards so that I could use the measuring marks on the board. Be careful if you do that because it’s very awkward and you can easily cut yourself.
Then, simply line your molds.
Step 3: Step 3: Mix Your Epoxy, Fill Your Molds, and Place in a Vacuum Chamber
I went with the kind which is commonly used in restaurants for table
and bar tops. It’s incredibly clear and has a much lower viscosity than epoxy you could purchase from a hardware store but also a much lower hardness. It’s probably ideal as it doesn’t smell, react with plastics, or require extra thinning but I would have liked a harder finish.
Mix your epoxy following the directions to the letter. Any wavering and you can end up with a subpar product. Then fill your molds. Mix only enough to fill however many molds will fit in your vacuum chamber. (note: read your epoxy directions before you build your forms. Some epoxies will react with certain plastics which are commonly found in hot glue. Epoxy also produces heat to varying degrees depending on the type used. This too could melt the hot glue.)
Once your molds are filled you need to make certain that each board has epoxy between it and the boards on either side. I used a ball-point pen ink tube to gently open the spaces between the boards allowing the space to fill. You MUST do this step. (note: it was suggested to use a wood stabilizer or CA glue to seal the boards first in an effort to reduce the number of bubbles emitted from the board. I tried a few pieces but was unable to get an even coat that would leave the flutes completely open. It also creates quite the mess, your results may vary.)
Then, place your molds into the vacuum chamber.
Draw a vacuum and leave the molds sit until cured, overnight seems to be long enough. From what I can tell, repeatedly drawing a vacuum and then letting air back in (pulsing the chamber) only introduces air into the epoxy. This creates an epoxy foam and is not what you want. The most effective technique was to pull a vacuum and leave it sit until cured.
Let your blanks cure for a minimum of 48 hours before turning. The instructions say 24 hours but I would play it safe and wait an extra day before turning.
Step 4: Step 4: Turn, Finish, and Assemble Your Pens
Because corrugated is a dry paper product it naturally absorbs some of the epoxy which leaves tiny air bubbles between the boards. This leaves the blanks incredibly weak as soon as you turn the molds off. I tried to turn all four of my blanks down to round and all of them broke except the aerated one which was fractured throughout. It is critical that you insert your pen tubes before you turn the pen.
This epoxy is also very brittle. When it breaks, it looks like broken glass minus the shards. Do your best to work slow to avoid hard shocks which stress the blanks further.
Following basic pen turning techniques minimizes this breakage.
Safety note: turning these blanks produces lots of fine dust and fumes. You should take all safety precautions when working with this material. In addition to a face shield or other eye protection and hearing protection you should wear a dust mask. When finished turning, immediately shower and place your clothes in the washing machine to get rid of the fine plastic dust that has accumulated on your person.
Cut your blanks into octagons to minimize the hard shocks of trying to turn from square. Then, cut your blanks to size, drill them, and glue and insert your tubes. The tubes help give the blanks some rigidity but you still want to work the blank very slowly and very carefully as I still broke one even with the tube.
I do not advise using tools to turn the pen completely down to the shape you want. I had better success leaving the blanks a little more full and finishing with 150-grit and 220-grit sandpaper.
Once your pen is in the shape that you want the next step is
finishing. Start with 220-grit sandpaper and then work your way all the way down to 800-grit followed by 0000-steel wool. With each step turn your lathe off and work end to end to remove any tooling marks caused by the spinning lathe.
You may notice tiny air bubbles which fill with dust from the sanding process. Do your best to wash these out with water, remount the pen on the mandrel, and spin to dry. If the holes are small enough they will fill with a CA glue rub. Larger holes require that you mix a small batch of epoxy, fill the holes, and sand them smooth once the epoxy dries. Note that this doesn’t completely solve the problem it only makes the holes smooth.
Once your CA glue finish has dried you can start the buffing process. I use a jeweler’s kit with diamond pastes while others use buffing pads. It’s up to you as both methods work well.
Then, assemble your pen.