Introduction: DREGS - Desk Refurbishment and Expansion: Glass/Silicone Surface

The donor.
A 1990s round steel tube framed desk with 5/8" MDF surfaces

  • Lower level: 35.875"x23.875" (reused)
  • Upper level: 35.875"x9.875" (scrapped)

The doofus.

A 1987 human with numerous deficiencies and a fondness of bizarre acronyms.

The upgrades.

  • DREGS - Desk Refurbishment and Expansion: Glass-Silicone Surface
  • TRAFFIC - Total Room Air Filtration and Forced-air Internal Component Cooling
  • MIRTH - Mixable Illumination Reconfigurable Tool Holder

The reasons.

The donor had survived many years of abuse by at least two kids, so the top surfaces of the MDF were not in great condition. The upper level was sagging significantly and was always located too close to the lower level, which greatly decreased the usable area on the lower level. In addition to the surface bubbling and scratches, MDF is also not well suited for the high temperatures involved in electronics assembly. I had been using some aluminum sheet to protect the surface from heat but that introduces a new and very dangerous hazard when working with powered electronics, so eventually decided it was time to update the desk.

In addition to upgrading the work surface with a heat resistant and electrically non-conductive material, I wanted to replace the upper level with a tool holder and storage unit placed at a greater height above the lower level to reclaim some usable work area on the lower level. I also really needed to add some air filtration to the room since I spend so much time in the room and there is always so much dust collecting on surfaces. I was initially planning to make an illuminated pegboard tool holder similar to the one made by CasperH on the trossen robotics forum, as I happened to have a sheet of scrap polycarbonate in the basement and I have quite a few RGB LEDs that could be placed behind it to great effect. Unfortunately, I had actually started this project in mid to late October but my anxiety and depression tend towards severe procrastination regarding any projects that might actually benefit myself. This tendency left me repeatedly sidetracked and ultimately required me to scale back the projects that were intended as additions to DREGS. TRAFFIC and MIRTH have been reduced to a single filter and blower that I can attach to the sections of tube frame that formerly supported the upper level of MDF and were supposed to support TRAFFIC and MIRTH. They will likely be completed in the future, but additional motivation will be required.

Step 1: DREGS - Desk Refurbishment and Expansion: Glass-Silicone Surface

The materials.

  • (6) 12"x12" glass mosaic squares with .75" tiles
  • (3) 10oz. tubes of clear GE Silicone II
  • (1) small bottle of acrylic paint
  • (1) 1.25"x1.25"x48" length of 1/16" thick 6063 aluminum angle
  • (1) 1"x1"x8' length of 1/16" thick 6063 aluminum angle
  • (1) box of 0.5" long wood screws
  • (1) can enamel spray paint

The tools.

  • Tape measure or yard stick
  • Automatic center punch or scratch awl
  • Hand drill
  • 1/8" drill bit for holes in aluminum angle
  • 5/64" drill bit for pre-drilling holes for wood screws
  • Disposable gloves
  • Stir stick and mixing surface
  • Cheap, wide putty knife

The prep-work.

First I removed the MDF boards and little steel angle brackets that helped keep the long wood screws from ripping through the thickness of the MDF. The top surface of the lower level was not in good condition but the bottom was unfinished and pristine, so I flipped the MDF and painted the bottom surface with the last of a can of spray paint (satin almond?). This MUST be done outdoors or under a fume hood as there are some nasty solvents involved.

After the spray paint had dried/cured, next was to add the aluminum angle around the perimeter of the 5/8" MDF. I started with the 4' length of 1.25" angle which would go along the back edge to help form a lip to prevent things getting pushed off the surface. I was a little surprised that the angle was scored on the inside of one leg, but it wound up being useful for keeping the screw holes in a consistent distance from the edge. I basically just lined up the tape measure against the groove and used the center punch to mark off every 2" starting from the center of the length of angle. After lining up the angle against the center of the back edge of the MDF, I used the center punch to scratch the leg of the angle where it would need to bend around the corners of the MDF. Using the scratches as reference, I measured out 1-3/16" in both directions (1.25" minus 1/16" of leg thickness that will wrap around the exterior) and used a straight edge (scrap aluminum) to mark/scratch the sides of the triangle cutout I would need to let the aluminum angle bend cleanly around the corners of the MDF. Better to remove a little bit too much of the angle than to remove too little. If too much material remains, you will not be able to get the inside edges of the angle to easily touch the outside edge of the MDF, which can lead to tearing of the aluminum when you force it. One back corner went well, the other not so much. One wood screw per two inches is overkill, but I had a box of many screws that would not likely be used for any other project any time soon, so why not? After getting the angle lined up against the MDF, I started at the center and used the holes in the angle to pre-drill the holes for the screws. I did not have a countersink bit, so the flat head screws do protrude some but that does not bother me. I also used a cheap hobbyking reamer to clean up the holes a little bit and got a reminder in how easily I bleed when a tiny sliver of aluminum pushed into the thick layer of skin just beyond the nail of my thumb. No pain going in or coming out, but lots of blood for such a tiny prick.

After getting the back edging completely attached, I butted the 1" angle against one end of the 1.25" angle and started marking off the 1" angle with the center punch at roughly 2" intervals on the first side with deviation from 2" spacing as required to keep at least 1" of space between the short screws attaching the aluminum and the long wood screws that attach the MDF to the tube frame. This ended up being 2", 4", 6", 8", 10", 12", 15", 17" from the corner going toward the butt joint of the two pieces of aluminum angle. The assembly process was much the same as with the 1.25" angle, where I first aligned and temporarily attached the short edge with two screws then scored the inside of the angle where it met the corner of the MDF. After removing the two screws to make the required cutout of the bottom leg, I then reattached the angle to the MDF with the same two screws and proceeded to bend the angle around the corner and score the inside of the angle at the next corner. Again removed the screws and angle to mark off and drill all the remaining screw holes in the aluminum angle, and make the cutout for the final corner. After the aluminum had been prepped, I reattached it with several more screws on the front edge and performed the final bend. The final cut in the 1" angle where the two pieces of angle would butt together was first rough cut with the nibbler then filed to meet cleanly. You could perform all of the cutting and drilling of the angle prior to ever attaching it to the MDF, but I am not known for my precision when using hand tools so chose to make it fit as I went. After everything lined up, I added the last of the screws to secure the angle.

Step 2: DREGS: Getting Messy Laying Tiles

Next was to mix up a big batch of silicone and lay down the glass tiles.

Wear gloves. Wear gloves. Wear gloves.

If you have access to a supply of proper two-part silicone rubber/foam, then this paragraph can be skipped. A proper two-part silicone should be used instead of GE Silicone II and acrylic paint as there will be much less guesswork and better results, but I went the the cheapo/bigbox route. While waiting for the spray paint to cure before attaching the aluminum angle, I started testing silicone and acrylic paint blends to get a better idea of what would actually work. GE Silicone II is a one-part tin-catalyzed RTV silicone that uses moisture from the surroundings to complete the curing process, while acrylic paint uses water as the solvent that must evaporate to allow the pigments to dry/adhere. The silicone creates an effective moisture barrier as it cures so we cannot use it alone between two large impervious surfaces or it will take a very long time (months to years) for enough moisture to reach the innermost volume to allow it to fully cure. The acrylic paint adds moisture to the silicone blend that permits it to fully cure even when using thick cross-sections and/or placing it between impervious surfaces. The references I found gave a ratio of roughly one drop of paint per ounce of silicone, but it can be difficult to judge a 'drop' if the acrylic paint is thick and gloopy like the stuff I had. So, it is better to initially add too little paint than too much, as more can be added later during mixing if the blend does not look right. If you add too much paint, then the blend will have poor adhesion and possibly never dry/cure because there is too much moisture sealed within the silicone, thus leaving you with a weak greasy mess and wasting the entire batch of silicone.

I mixed the silicone a bit like making noodles by pouring the three tubes of silicone into a mound on a piece of scrap metal then mixing in the paint with a stir stick and putty knife. Basically, stir for a while then scrape the silicone off mixing surface near the edges of the mound and flip/fold that onto the center of the mound and push it downward and outward. Repeat until the paint is well blended into the silicone. I did not de-gas the silicone blend, partly because I did not have a vacuum pump and partly because I did not need extreme tensile strength as would be needed if it were intended to be the tread of a wheel. Having air entrained in the blend would also improve the insulating property to the silicone which is nice as the surface is going to be used for electronics assembly (soldering iron and hot-air rework station).

After mixing, I basically just scraped the mass of silicone onto the MDF surface with the putty knife and pushed it toward the edges to ensure full coverage. I did not do a very good job of getting a consistent thickness across the entire MDF surface prior to applying the tiles and probably should have used four tubes of silicone instead of three since there was not enough to completely fill the gaps between the tiles. I did make sure to use enough pressure when spreading the silicone onto the MDF to ensure there were no bubbles between the silicone and MDF as that would greatly decrease the bonding strength between tiles and MDF. It is pretty easy to spot bubbles in the thin silicone as they look it has torn or sheared off in that area. Once the silicone was relatively well distributed, I started placing the tiles at the front left corner and used slight pressure to get the bottom of the tiles coated in the silicone blend. Unfortunately, I did not test fit the tiles prior to applying the silicone, so did not realize that the tiles were just a little too big for the surface. The tiles ended up crowded vertically where they meet in the center and I had to remove one column to get them to fit horizontally. Once all the tiles were relatively well positioned on the surface, more pressure was applied to the tiles to fully place them in the silicone blend. This was done with a short segment of an empty silicone tube wrapped in a very damp paper towel to prevent the silicone adhering to it. The water in the paper towel causes the silicone to form a skin that prevents it adhering to the paper towels or the tube, but does not interfere too much with the silicone adhering to the bottom and edges of the tiles. I basically used the tube as a roller to push the tiles further into the silicone and then used gloved fingers to push down and align any stray tiles. After the silicone had cured for several hours, I mixed up another batch of silicone to fill in the spaces left between the tiles due to insufficient silicone on the MDF surface when initially placing the tiles. It was mixed in the same manner as the first batch and I just used the putty knife to apply it to the entire surface and squeeze it into all the remaining cracks. Excess silicone was pushed into the edges to form a transition from the tile to the top of the aluminum angle.

Not super pretty, but works well enough for however many years the silicone survives.

Step 3: DREGS: Reassembly

After the tiles were set and silicone cured, the lower level was finally ready to be remounted onto the steel tube frame with the six long wood screws. Prior to this, the frame was disassembled and re-assembled in a slightly different manner because the tube that joins the two sides together was at just the right height and depth to cause my shins many troubles. With that tube flipped, it forms a nice foot rest and does not significantly affect the stability of the desk. A bit of silicone was added between each tube at the mating surfaces and the bolts partly tightened to provide a slight amount of isolation between each tube to stop the squeaking/creaking it had previously exhibited with metal-on-metal contact. The bolts were further tightened after the silicone had been left to cure for several hours.

Step 4: TRAFFIC: Being Cheap With Air Filters

The materials.

  • (1) 24"x24"x1" pleated air filter
  • (1) cheap foam brush for applying glue
  • (1) ~2"x~26" piece of scrap cardboard
  • (1) bottle glue (e.g. Titebond wood)

The tools.

  • Heavy duty serrated scissors or tin snips

The process.

As it seems common for many stores to list all sizes of air filters of a given filtration rating and brand at the exact same price, I decided to be cheap and turn a single 24"x24" filter into four 12"x12" filters. Basically, just use a pair of heavy duty serrated scissors or tin snips to chop the 24" filter into four equal sized pieces. After that, get some scrap cardboard (I used empty cereal boxes) and cut it to size, fold it, and glue it to form new borders/reinforcement for the smaller filters. I used wood glue and a foam brush to bond the cardboard to the filter, as that was what I had on hand. The wood glue needs to be spread very thin to keep it tacky and not saturate the cardboard, which will make the cardboard curl/deform. The bonded cardboard border is necessary for pleated filters to achieve a decent seal in the filter holder/housing, otherwise air can easily pass around the edges of the filter. The end result does not have to be pretty, as my attempts make clear.

Step 5: TRAFFIC: the Filter Housing and Blower

The materials.

  • (1) 120mm fan (Delta AFB1212SHE: 151CFM, 12V/1.6A, 54dB; $5 at Surplus Center)
  • (1) 12V/+2A power brick
  • (1) 12"x12"x1" pleated air filter
  • Polycaprolactone (PCL) (Instamorph, etc.)

The tools.

  • Microwave, hot plate, or stove

The process.

If using a microwave, place the PCL in a large glass or ceramic bowl with a fair amount of water, then heat in 10~15 second intervals checking for the pellets to appear clear/transparent throughout their volume. If using a hot plate or stove, use a metal pot/pan filled with several cups of water and heat to boiling over high heat then drop to low heat before adding any of the PCL pellets to the water. Gently stir until the pellets are transparent throughout their volume and scoop them out onto a plate or bowl to cool and drip dry for a little bit of time before trying to form it.

Although it is potentially very dangerous, I have a tendency to not bother with the water when heating PCL in a microwave. As you heat the PCL, you will get a molten shell on a solid core. The water acts as thermal mass to moderate the temperature of the PCL and prevent excessive heating that can ignite the molten PCL. Instead of adding water, I simply place the pellets in a bowl (or pre-formed/reused slab directly on the glass plate of the turntable) then alternately heat and sit in 10~15 second intervals. Leaving it to sit (or stirring it) for several seconds allows the heat added to the exterior of the PCL mass to travel further into the interior of the mass instead of overheating the molten exterior.

Once you have a sufficiently large and pliable mass of PCL, start forming it into a cone/pyramid with one end having a 12.25" square opening for holding the filter and the other end having a 110mm circular hole in a 4.5" square for mounting the fan. The PCL will become increasingly stiff and translucent as it cools, so you will get an idea of how much time you have left to work with it before needing to reheat it, if necessary. After formed into the cone/pyramid, the filter should fit easily into the 12.25" square opening and the blower should line up relatively well with the 4.5" square and 110mm hole for mounting with some screws. The blower spins only in one direction, so make sure the intake side is pointing towards the filter so you do not get lots of dust accumulating on the blades of the blower. Wire the blower up to a 12V power supply capable of at least 1.5A and it is finished.

Depending on your outlook, it may be a good thing or bad thing that I do not yet have any pictures of my initial attempt. I expect most people would prefer not having their eyes bleed from the visual horror.

Comments

author
Modern Rustic Workshop (author)2017-01-03

Very cool and I love how you conserved the air filters to make the most of them!

author
tjdux (author)2017-01-03

Hi that's a nice looking work desk you re purposed. I'm curious why you used the silicone/latex paint mix instead of just getting a few tubes of construction adhesive? also they make glue spreaders that have little teeth that make spreading glue to a consistent height really easy and I think it may have made attaching the tiles easier for your desk top.

author
tician (author)tjdux2017-01-03

Basically wanted to try out casting with cheap silicone and acrylic paint for possible use in robot tires and/or potting electronics. It is also flexible compared to standard grout (very important with cheap MDF base material) and very heat resistant compared to latex grout. The ability to make it any color desired is also rather nice... A toothed spreader may have helped a bit, although one of the reasons I
wanted to use silicone was to simply pour it on the MDF and have it
flow upward to fill the gaps between tiles without any effort besides
setting the tiles in place. Unfortunately, I did not use enough silicone
to have that work out as I wanted. Not sure how well my silicone+paint blend is actually going to work in
the long run, but it should last at least a few years of abuse before any tiles start pulling out. Will hopefully have the income to afford a proper two-part silicone by the time the tiles need to be removed, cleaned, and reset into a fresh batch of silicone.

As for the gap in your shower, many thin layers of plain silicone would probably be better for sealing against water. Just let it cure for several hours (preferably 24+) between adding each layer, so that there is enough time for moisture from the air to penetrate into the silicone before sealing it off with another layer.

author
tjdux (author)tician2017-01-03

Regular silicone and silicone 2 won't adhere and cure properly when applied on top of existing cured silicone according to the label of the actual silicone itself. Also on the labels it states that silicon will not cure properly if laid deeper than half inch thick which is why I'm interested in trying the paint mix you exposed to me to allow thicker beads.

author
tician (author)tjdux2017-01-03

Adding acrylic artist/hobby paint or glycerine will decrease the adhesive properties of the silicone, which is not great when trying to seal against water on a smooth impervious surface like metal, glazed tile, or finished fiberglass+resin composite. Probably best to just use some sort of filler or backing strip to keep the layer of plain silicone thinner than 0.5" from the top surface of the shower.

author
tjdux (author)2017-01-03

Also I may look into the idea of using the paint silicone mix for a home project I have coming up. Fly by night contractor did a terrible job installing our shower and it needs a bead of silicone a inch tall and almost .75 inches think which is more think than silicone should be spread, to keep it from leaking into tbe basements at tbe joints.

Oh one more thing maybe some.more pics of the end results especially the filter and such.

author
Swansong (author)2017-01-03

This looks really nice :)

author
tician (author)Swansong2017-01-03

Thanks. It would look even better if I had used more silicone in the initial application and done a better job of spreading it to a uniform thickness prior to placing the mosaic tiles. Ideally, I would have used a lower viscosity two-part silicone blend that I could just pour onto the MDF then shake/thump it (like batter/dough in a pan) to get it to evenly distribute. Still much better than the plain painted MDF.

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