Tag Archives: laser cut

108: Preparing Laser Cut Wood for Paint

Scott at work!  Mixing the green wash (there is a touch of gel medium in the glass too)
Scott at work! Mixing the green wash with our trusty note taking and testing plate.  

This month I thought it would be fun to add a new skill: properly preparing a wood surface for painting.  I have painted laser cut wood in the past (Week 64 is a notable example), but honestly, the preparation and finished result is not what I’d consider fine art.   So, with the help of Scott Sherwood, Fine Art Conservator, we will learn some basic first steps to preparing unfinished laser cut plywood shapes for paint.

week 108

Supplies you will need:

  • Laser cut wood shapes
  • Grain filler (I picked up DAP Plastic Wood from the local DIY store)
  • Scraper or palette knife (we used a metal spatula!)
  • Gesso (Liquitex is Scott’s favorite, easily attainable brand)
  • Water
  • Paper Towel
  • Brushes
  • Foam roller
  • Sandpaper (240 or 400)

Step 1:  Cut your shapes

Our professional work surface
Our professional work surface. Apologies for the poor photos – I was not using my own camera, and we hopped from natural light to fluorescent light too much.  Another lesson learned!

For ease, I precut some plywood into shapes I had on file – a bird, the whale and a couple different quatrefoil examples.  I also had a couple plywood circles left over from an earlier project and threw them in the mix.  Cutting first means the edges will get some over paint and need to be finished at the end – if that is a problem or you have a particularly intricate shape, I’d suggest preparing the surface and possibly even applying the background color before cutting.

Step 2: Determine whether you have open grain wood or closed grain wood

Closed grain on the left, open grain on the right
Closed grain on the left, open grain on the right
Raking the light across the surface makes uneveness pop right out
Raking the light across the surface makes uneveness pop right out.  The ampersand wasn’t cut for this project, but something I had laying around.

Some wood simply has more prominent grain than others.  Oak is a prime example of open grain wood.  The shapes I specifically cut for this project were on closed grain (I believe it’s birch ply), but the circles were open grain oak ply.

Like buttercream frosting :)
Like buttercream frosting 🙂
Post filled and sanded disks. They are amazingly smooth!
Post filled and sanded disks. They are amazingly smooth!  The lighter spots are the fill.
Side angle on the sanded disks to better show texture.
Side angle on the sanded disks to better show texture.

Open grain needs to be filled in order to achieve a smooth surface, and that is where the DAP grain filler comes into play.  I purchased it in a tube, and it comes out like a putty almost.  We slathered it on against the grain, making sure it got into the pores of the wood.  Scott said “fill it proud!”  Well, we definitely did – it looked like we frosted cupcakes when we were done.  In retrospect, we make have over filled, and I would probably have thinned the paste a touch with water to make it easier to work with.  Live an learn!  Wait for it to dry (it was thick, so we waited 24 hours) and then sand off the excess.  You sand enough that you want to see the prominent grains, but it will be smooth as glass.

Picking up a closed grained wood allows you to skip this step, which I would recommend unless you wanted to look of oak or a specific open grain wood on the back.

Step 3: Acrylic Gesso Wash

Gesso, for those that do not know, is a priming paint.  There are versions for painting with oil paints and for acrylic paints.  Oil paint *can* go over acrylic gesso, so, for versatility’s sake, we used acrylic gesso.  It is made with white pigment, chalk, an acrylic binder (to make it a liquid) and a smattering of other chemically stable elements.

Why prime your wood with gesso?

  • It creates a uniform,  layer under the paint
  • It gives you surface a nice “tooth” to hold paint
  • It keeps paint from soaking into the material underneath
  • It protects the paint from chemical changes on the board underneath – wood is organic, and the process they use to create plywood is not exactly archival.
It's hard to see in the photo, but the gesso wash is pretty frothy!
It’s hard to see in the photo, but the gesso wash is pretty frothy!
Wiping away the gesso wash
Wiping away the gesso wash

You can slap the gesso on, undiluted, but it really doesn’t penetrate the wood very well.  We mixed up a gesso wash, which is gesso + water.  It may have been a 50/50 ratio, I should have been measuring!  But you want it nice and runny.  We put it on with a foam brush.  You can also use your fingers if you like a more tactile experience.  We really smushed it on, working it into the grain of the wood, which created a sort of foamy looking paint layer.  When we were satisfied with had penetrated well, we wiped off the excess paint with a paper towel.   Let dry thoroughly.

Step 4: Light Sanding

The gesso wash soaked in well, and caused some of the grains of wood to swell, and the dried surface was slightly uneven.  We hit it quick with some 400 sandpaper to smooth it out.  It’s not uncommon for artists to sand between each prep layer – it gives a nice even finished look.

Step 5: Full Strength Gesso

This is the step where the ground work you lay down has a stronger effect on the finished piece.  Scott suggested a couple different ways to incorporate texture with the gesso layer on the laser cut shapes:  with brushes, or with foam rollers.

Swirled whale texture
Swirled whale texture
Flowing bird texture
Flowing bird texture

Full strength gesso has the ability to hold some texture; it’s not self leveling as a more watery version would be.  We took brushes to the whale and the swallow.  I made swirls of gesso on the whale, trying to emulate a turbulent sea.  Scott chose to paint gesso on the bird with long, flowing brush strokes, to evoke the feeling of flight, or airiness.  The subtle peaks and valleys of the gesso will still be present behind whatever paint it will have in the end, adding a depth.

First layer of the foam roller texture
First layer of the foam roller texture

The more geometric shapes for the foam roller treatment.  Rolling on the full strength gesso created a fabulously fine pebble texture, almost like vinyl.  The first layer looks suspiciously like a popcorn ceiling treatment, but it calms down with repeated applications

We let all the pieces dry overnight.

Step 6: Repeat Step 5 as necessary

Everyone has different goals for their primer, and different levels of “done.”  We put a second coat on, and looking as I’m writing this post, I’m tempted to do a third.  As it dried (and sadly got got banged up a bit when I cleared off the table they were on) imperfections became clear – the brush lines weren’t exactly where I wanted them, or had areas where the vinyl-like texture was less pronounced.  If you want, you can also do a quick sanding between each coat of gesso – it’s up to you and the finish you want!

Step 7: Add art!

When you feel your board is primed properly – but that, I mean it has even coverage of gesso, a good texture and reminded me of a sheet of really nice paper that I was itching to put my pencil to – you are ready to add your art.  I didn’t intend for the project to go to the actual art stage, but Scott and I were experimenting, and I couldn’t resist picking up a tube of “sap green” acrylic when buying the gesso (colors are so PRETTY.)  Here are three different paint treatments you can do:

From left to right: Wash, glaze and tint. It's amazing these greens all came from the same tube of acrylic!
From left to right: Wash, glaze and tint. It’s amazing these greens all came from the same tube of acrylic!

Wash – We mixed the acrylic paint with water, which created a very flowing semi-transparent layer of paint.  It was very light in color and was very wet.  If we were using oil based paints, we would have used turpentine to thin it.

Glaze – Glazed are made when a color is added to a “transparent gel medium.”  I’m not 100% sure what the medium is made of, but the color was really vibrant.  Glaze is nice because it is translucent – light can penetrate the layer and make it really pop.

Rolling on the tint.
Rolling on the tint.

Tint – here we mixed white gesso with the acrylic and came up with a lovely minty green.  It is opaque.

The gesso base is also good for charcoal, pencils, pastels, oils, even mixed media or collages.  It’s a good standard base to build on.  Today, most painting is done on canvas, but it actually wasn’t until the 16th and 17th century canvas became popular.  By painting on panels, you are paying homage to an old tradition (even though the panel was cut with new technology!)

This post is in no way comprehensive (even though it is the longest one I’ve ever written!), and it’s one professional’s opinion.  Artists come to develop their own style and preparation methods they like – experiment!  And enjoy!

 

107: Thick Acrylic

A few months ago, my friend Arty got in touch with me and said he had “some thick acrylic” left over from a recent storefront revamp at a mobile phone store. Not really knowing what I was getting into, I said “hey any scrap material that I can laser is good with me!”

This stuff is so clear it's almost hard to see.
This stuff is so clear it’s almost hard to see.

Much more recently, I went to pick up the acrylic that he’d been graciously holding onto for me. As it turned out, the acrylic wasn’t just thick. It was far thicker than I could process with the laser, with 7/8″ as the thinnest edge. But there were several chunks of uniformly cut acrylic, and every surface was smooth enough that you could see clear through to the other side. This was material worth experimenting on!

The first engraving test confirmed that it was cast acrylic.
The first engraving test confirmed that it was cast acrylic.

I first determined whether it was cast or extruded acrylic by doing a surface engraving featuring some art deco frame stock. The surface engraving was powdery and white, which was perfect—cast acrylic engraves in a much more visible manner than extruded acrylic.

The second design didn't really convey the "frosted ice" look I was going for.
The second design didn’t really convey the “frosted ice” look I was going for.

The second design I tried was based on a “frosted ice” theme I developed while working with a client a couple of years ago. While it looked great on the snowflake shapes I used originally, the effect was lost on the square chunk of acrylic, and the “FROSTY” text I added didn’t really come out clearly.

Two different sizes of blocks "comprised" of tetriminos.
Two different sizes of blocks “comprised” of tetriminos.

I revisited some tetrimino patterns from a very early 52LASERS post. Using three different engraving techniques, I created a pattern that highlighted certain shapes with fills and deeper cuts. The result not only looks awesome from straight on, it created some really stunning effects when looking through the unengraved side of the acrylic.

Looking through the clean edge shows off each "deep cut" tetrimino.
Looking through the clean edge shows off each “deep cut” tetrimino.
Any fan of Tetris will recognize these shapes!
Any fan of Tetris will recognize these shapes!

I still have plenty of stock of these blocks left, so if you can think of any more creative ways to jazz up the acrylic’s surface, let me know in the comments!

Quite a supply of material too thick to cut through!
Quite a supply of material too thick to cut through!

100: Pyramid Holograms

The pyramid, taped and ready for the phone.
The pyramid, taped and ready for the phone.

A few months ago,  Jennifer had me order some unusually thin 1/32″ transparent acrylic to try out some kind of “phone hologram” trick she read about on the Internet. The material arrived in a shipment of a whole bunch of other inventory and was mostly forgotten, until just last week Eagle Engraving’s resident laser ninja Monica brought up the same concept and basically demanded I make it happen. So thanks for helping us reach the big 1-0-0, Monica!

A close-up of the pyramid.
A close-up of the pyramid.

The pyramid hologram uses four pieces of thin transparent acrylic taped together in order for it to be placed either on top of or below a display—in this case, a mobile phone. A specially formatted video is then played back and the image is reflected “into” the pyramid, resembling one of those old Sega arcade “hologram” machines.

There are plenty of templates out there on the net to make your own, but I followed the graph paper measurements from Demilked. The laser did the dirty work, replacing the most often recommended x-acto knife work on a CD jewel case. The finished plastic was very clean, but my questionable tape job connecting the four trapezoids left things just a little sloppier. Even with the pieces taped, the pyramid is a little wobbly, so I had to be gentle when balancing the phone on top.

Tiny minions make jokes underneath my Moto X.
Tiny minions make jokes underneath my Moto X.

While you can also rest the finished pyramid on top of your phone, I opted to set the phone on top so I’d see less of the originating video. There are several videos on YouTube to demonstrate this trick, and you need to choose “screen up” or “screen down” versions to make sure the hologram is displayed correctly. With the phone on top, I selected a playlist of screen down videos and set it going. Minions, anime girls, and a very motivational Shia Labeouf all appeared in my tiny pyramid and danced around. All in all, it’s a neat little trick, and didn’t take much time; perfect for a busy holiday season!

Hatsune Miku shows off a double image effect that's hard to avoid.
Hatsune Miku shows off a double image effect that’s hard to avoid.

98: Breaking the Interlock

One of the projects I’ve been working on this week involves some pieces of wood that are far bigger than my laser bed allows. While I’m not finished with the project yet, I thought I’d take a moment to talk about the front door on my VLS 4.60 laser and a fairly simple trick to defeat their magnetic interlocks in cases where you have to engrave something too long for the laser bed.  First, here’s some quick information about the project.

Here are some screenshots of the original box.
Here are some screenshots of the original box.

Those big long wooden pieces are for a custom frame design (by If These Walls Could Talk; check ’em out!)  meant to fit a picture of the Leg Lamp from A Christmas Story. The test piece given allowed me to perform a handful of engraving tests to determine how best to replicate the fragile (it must be Italian!) label on the Leg Lamp’s box.

Several engraving tests have convinced me that I need some spray paint.
Several engraving tests have convinced me that I need some spray paint.

One immediate issue was that the surface of the wooden frame pieces was darker than the inner wood, so even engraving at a high power and low speed to char the wood resulted in text that wasn’t appreciably darker than the wood, while the source material was black spray paint on lighter wood.

Color fill seeped under the masking paper too easily, so spray paint is my next test.
Color fill seeped under the masking paper too easily, so spray paint is my next test.

I then tried some paint fill, but the strong texture of the wood meant that my transfer paper wouldn’t prevent the color fill paint from seeping. My next step will be to try a light spray paint over another paper masked engraving; it should more closely approximate the look featured in the film.

The three edges of the frame I am to engrave. One is a tight squeeze, and two more won't fit at all without leaving the front door open.
The three edges of the frame I am to engrave. One is a tight squeeze, and two more won’t fit at all without leaving the front door open.

But the biggest trick here was figuring out how to fit those larger pieces of wood into the laser. When we were first looking into buying the laser, another laser owner mentioned how the front door interlocks could be defeated to allow people to engrave larger items—like boat oars—if necessary. I never heard from him how to do so and the manual doesn’t mention it at all. Doing this is considered a potential safety hazard, too, for quite a few reasons. The manual explains the following:

DO NOT OPERATE THE LASER SYSTEM IF ANY SAFETY FEATURES HAVE BEEN MODIFIED, DISABLED OR REMOVED. This may lead to accidental exposure to invisible CO2 laser radiation which may cause severe eye damage and/or severe burns to your skin.

The left interlock magnet, tricked by a badge magnet.
The left interlock magnet, tricked by a badge magnet.

With that in mind, defeating the magnet interlock is something you do at your own risk. Do your best not to look at the laser or stick any body parts in there. Also recognize that the exhaust system will be compromised to a certain degree as it’s no longer a closed system.

The right interlock magnet and some of the wood sticking out of the front door.
The right interlock magnet and some of the wood sticking out of the front door.

The front door is held by one magnet on each side, and there is a sensor behind each magnet that detects whether the matching magnet built into the door is present. While some of my weaker magnets weren’t able to trick the sensors, a pair of stronger badge magnets, positioned just right, were able to convince the machine that the front door was closed. My counterfeit badge magnets were attracted to certain parts of the laser body’s magnets, and when I let them slide into where they wanted to go, the sensor could no longer pick them up, so I had to arrange them sticking out (as shown in the pictures) in a very specific position. With this in mind, be very careful when processing your long materials, as nudging the magnet just a tiny bit can cause the laser to realize the door is open and stop the job immediately. For all the trouble that might cause, I’m certainly glad it’s designed to shut jobs down if the doors are opened mid-process.

I hope to write a follow-up post about this project once the frame is built around the Leg Lamp picture; I haven’t even seen the piece it’ll frame yet! Until then, have fun engraving longer materials, but be very cautious when breaking your laser’s interlocks.