Powder Coating – Mark Bronkalla

Path Lights – Powder coating and final assembly

Now that the lights have all of the pieces soldered together and cleaned up, it is time to cut the stems and get everything powder coated.

You need to be sure you have calibrated your oven and are sure of the actual temperature vs what is set. Additionally the parts should be placed to the sides, and not in front of the fan. The problem is that the powder coating cures at temperatures very close to (if not exceeding) the melting point of the solder. So it is very possible to have your assembly fall apart or significantly change shape while curing the powder coat. Below is a chart I pulled from the Kester web site: https://www.kester.com/Portals/0/Documents/Knowledge%20Base/Alloy%20Temperature%20Chart.pdf As you look at the chart, the solders we have commonly used for electronics, stained glass work and plumbing in the past are referred to as the “mid temp solders”. Note that the lower end of their melting range is 361F. The more modern lead free plumbing solders that I have run across are the Sn97Ag3 , and SN96.5, Ag3, Cu0.5. These have melting points above 420F. This gives us a TINY bit of wiggle room above the curing temperatures required for the powder coat.

So far I have used powders from Eastwood and Prismatic Powders. The Eastwood powders typically recommend 460F until the powder starts to fuse and then 400 for 20 min. This does not work with solder as I demonstrated with my first test piece. The solder joint (60/40) opened up during the curing. This lead to some more research and there were a number of posts that said a powder that cures at 400F / 200C for 10 min (as the Prismatic powders I was contemplating) could also fully cure at 355F/180C for 15 min. Note that this is not from Prismatic (I should really contact their tech support for confirmation). I ordered the candidate Prismatic powders and ran some samples. Sure enough, the powder seemed to cure very nicely at the reduced temperature (nice gloss and the metallic flakes glistened). My oven was calibrated against a Thermoworks Chefalarm and an IR thermometer. It runs +5 to -20F vs the set temperature once warmed up and allowed to soak for 15 min. I also decided to avoid placing any parts directly in front of the fan but rather off to the sides. I assume that the hot air coming from the fan is likely hotter than the “overall” oven temp. I had switched to using “lead free plumbing solder” to assemble the parts. The chosen powder coat was Prismatic’s “Soft Misty Copper UMB-1352“. So now was the time for the test of a complete lamp. This was the prototype path light. Everything held together and the finish was great.

So this proved that you CAN powder coat soldered parts. However, you MUST be careful in you choice of powder, solder, and oven calibration. There is little room for error and oven temps often swing +-20 to +-30F with greater swings during warm-up or when re-heating after opening and inserting the parts. It may be a good idea to line the bottom with fire bricks or tiles for more thermal mass, but I have not tried it. I did get all 8 lights powder coated without incident.

Prior to powder coating, the parts need to be bead (sand) blasted. I am using 80 mesh glass beads at 45-50PSI. The reason the pressure is so low is that the beads will fracture – turning to dust if the pressure is too high (increasing your materials cost) and the brass will deform under the pressure of the blast. This is most notable with the brass U which should be blasted at an oblique angle. Blasting straight on, can completely deform and close the channel. Once the parts are bead blasted they are then blown off with an air gun and hung on stainless wires from the oven rack.

The process of bead blasting and powder coating can be seen below:

Bead blasting and powder coating the lights

While my powder coating setup is a bit low tech, I am pleased with the results .

The lights get a bipin socket for the LEDs hotmelt glued into the base plate . Extension wires are soldered on. I used 5 watt LED “corncob” style lamps. These run off of standard 12 VAC low voltage wiring (and are darn bright).

The posts / standards are 21″ long 1/2″ copper pipe. This was the longest length that would fit horizontally in my oven for powder coating. They are rather tall, but this is needed as my old lights would repeatedly get buried in snowdrifts in the winter. The “anchor post” was made from 1/2″ galvanized iron pipe. I used 24″ sections, cut in half, ends split and then pounded to some semblance of a point. The same 1/2″ copper to 1/2″ threaded adapters that were used under the base of the light were also used on top of the stake. It is not necessary to solder the posts together. The friction fit with a bit of powder coat overspray is more than tight enough.

I found some new screw together vampire tap connectors that worked out very well to connect into the existing 14 gauge cable that was left from the old lights. These are far better than others I have used in the past.

I think the finished lights look great and are a definite improvement over the several previous light sets.

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Path Lights Concept

We are on our 4th (or more) generation of path lights for along the front walk and driveway. We live in the country and there is no street lighting. So we need path / landscape lights to provide illumination for safety (of course nothing is level here) and it just looks nice. However the commercial lighting products are pretty cheap and flimsy unless you are willing to spend hundreds of dollars per light. We have the wiring in place and a large 12 v transformer from the initial incandescent path light installation. We had converted to LEDs a while back but want things a bit brighter. Besides the current lights are again falling apart and the glass is breaking either on its own or due to “incidents”. Solar / battery lights are nowhere near bright enough and the rechargeable battery replacement is an ongoing expense.

So now it is time for new lights (again). Being recently retired, I have the time to pursue this, after getting more pressing projects out of the way. I started researching looking for designs that i could use as a starting point and to show Teal as I needed her approval. The lights will be mounted on top of 18-24″ posts with some sort of spike anchor base. We started closing in on some promising ideas and then it was time to start making prototypes out of construction paper. This would allow us to see the final size in the garden setting and help inform what the construction process would entail. I had decided to use copper and brass for the shell of the light and a cear “hammered” finish stained glass for the panes. LED light would be used. The metal would then be powder coated. The initial batch for the front walk will be 8 lights. If this works out well then 10 or 12 more will be needed for the driveway.

I wanted something of an Craftsman or “English cottage” sort of look with a peaked roof and 4 or 6 sides. So the first things to tackle were over all size and the roof design.

The first prototype looked like this.

It was a start and could be made in copper but the look was not quite right. I wanted a curved / flared roofline, reminiscent of a thatched roof. The copper foil / flashing I had on hand was also flimsier than I wanted. So purchased a roll of 12oz copper flashing to see if that would be thick enough. Then it was time to play with the roof design to see if I could get the look that I wanted and that Teal would agree with. More time was spent with paper, straight edge, compass and french curves. Now I had 3 paper roof prototypes.

We ended up choosing the middle shape. It has the flare I wanted but I was still debating which one. . Teal did not like the slightly upturned corners of the one on the left. So she had the deciding vote. As it turns out fabricating the curved roof in the middle was hard enough.

More materials were ordered. My old stained glass supplier was out of business and I had to try a new one. THis is where I got a few varieties of brass came and the class itself . More metal was ordered from SpeedyMetals for the bottom panel. I ended up using sheet brass for the bottom.

Now was time to start the fabrication and build the tooling. The Press Brake was already done but more was needed.

The prototype light looks like this.

I’ll cover the construction details and tooling next.

Next: Ring Roller dies for the roof corners

Exterior Light Refinish

Our exterior lights were looking pretty shabby. The original antique / brushed brass was tarnished and dull. 26 years of UV damage had destroyed the original clear coat. There were house paint splatters on them as well.

This is one of the smaller lights, by my shop patio.

This was also the first major powder coating project after the test pieces. I figured that getting a home improvement project done before tackling the workshop powder coating projects would help win some brownie points and help justify the equipment investment.

The lights are made of thin brass stock. The knurled balls on the corners and for the removable top (for light bulb change) were about 50% frozen on due to rust. They are screwed onto about 1.5″ pieces of threaded rod which were crimped into the corners of the lights. So in the cases where they were stuck the threaded rod came out as well. This allowed fo disassembly of the class panels and removing of the top. From then on it was a matter of starting at the finials and working my way in. Each rounded section had its own nuts and / or coupling.

Some parts, notably the threaded rod pieces needed an electrolysis treatment to remove the rust or corrosion. The parts were then bead blasted to remove all of the old finish and corrosion. Bead blasting for each lamp took about an hour. The small parts were mounted to a piece of masonite so they could be held while blasting. A wire was zig-zagged on the back side to connect all of the parts for grounding while powder coating.

small hardware on board after powder coating

Back side of the small hardware board showing the grounding wire and retaining screws or nuts

This board was simply placed on the bottom of the oven for baking or on the lowest rack. The other parts were hung via stainless wire from oven racks for powder coating and backing. Please remember to wear a dust mask / respirator while powder coating and blasting. The dust is a really nasty lung irritant. I neglected this at first (like you see in many of the youtube videos), and my lungs hurt for 3 days. Now I use my Miller Eclipse P100 respirator religiously when doing the blasting and powder coating.

The many other flat and domed pieces were hung prior to coating and there are a few important tips:

Only load 1 or 2 parts at a time prior to spraying the powder. Having a rack full of parts limits your ability to maneuver the gun and get even coverage. Load 1 or 2, spray, load a couple more, etc. Besides the overspray will help finish build on the previous parts.
Add a ground clip to each part rather than relying on the hanging wire and rack for grounding. With the lamp parts the center hole is an ideal point to add a clip lead ground. It wont show later, it is easy to coat after clip removal and you can get some leverage from the insides of the domes when removing the clip. I bought a new batch of alligator clip leads for just this purpose.
Hang the bigger parts with 2 wires. They WILL swing as you load them into the oven and this will lead to bare spots where the powder is knocked off.
Don’t be greedy and overload the rack with lots of parts. They will swing and bang together leading to bare spots and other defects. 4-6 at a time seems to be the limit. 8-10 is just asking for trouble. The bake time on these thin parts with the powder I was using – Eastwood Architectural Bronze is only 23-35 min (20 min after the part hits 400F). So you can still do over 2 batches per hour and have a nice break in between.
It is better to transfer full racks of parts in and out of the oven rather than singles and trying to hook them on and off individually (or maybe I am just a superb klutz with limited motor skills).
If possible hang the parts with >3″ and preferably 4+” gap from the rack (another variant of “don’t get greedy”). You need the space and don’t want to be spraying downwards through the rack if at all possible.
The corollary to this is don’t push your air compressor too hard with long bead blasting sessions. My DeVilbiss “6 HP” 60 gal unit gets really hot after 30 min of continuous run time (which happens while bead blasting even at 50 PSI reduced pressure to not cause the beads to disintegrate). At that point, the air is hot going into and out of the tank. Then the moisture (and oil) make it past the moisture separators and start showing up as discoloration on the parts while blasting. That is the signal to stop and let things cool down. The blast cabinet requires 9-12 CFM @ 50PSI for glass beads continuously while blasting (far more than a spray gun). I don’t have a chiller / condenser for the air lines (another $700+ investment) which would eliminate the condensation issue but not the overheating compressor .

Oven before I switched to a special rack for the panel dividers which are laying on the non-stick foil

Lamp parts hanging after initial fusion of the powder coat

First 2 domes attached Note the spacer bracket between the pipe sections

Cushioned pliers to attach nut and threaded rod. Blue tape or electrical tape work well to avoid scratching the parts.

I used a variety of textured clear “stained glass” to replaced the old beveled glass panels. I like the look of the textured glass better than the clear. Plus I did damage a few of the beveled glass pieces slightly during disassembly. The glass cuts are simple straight line snaps. However the seedy glass often deviates a bit from straight if the cut is near the bubbles. So a glass grinder or coarse grit diamond stone is a big help. I had not done any stained glass work for a few years. The internet supplier I had used previously used, was out of business and Milwaukee Art Glass is currently only open by appointment (as I found out on arrival). Some of the glass came from Hobby Lobby (which I detest, but is the only other local alternative I could find). Aside from the philosophical and general quality aversions, the small sheets they sell, would only yield 3 panels (and I need 6) per light (and there were 5 lights) with a lot of waste. However, some may be usable as I do the upcoming path light project.

Overall, this was a very satisfying project while building a variety of new skills. Replacing these lights with new ones would have cost much more than the powder coating equipment investment. There were 5 lights in all. Next up will be new scratch built path lights for the front sidewalk.

Aside from new tools, material cost for the 5 lights was:

Glass bead blast media ~$20 for about 10 lbs consumed
1 lb of Architectural bronze powder coat powder $12.95
Glass ~$50 – mixed sources
New LED lamps from Menards (FEIT 100w equivalent) $25

Powder Coating Startup

I have been interested in doing powder coating for a number of years but this does entailaddtioinal equipment and space (and spousal buy-in). I have been frustrated with conventional finishes (paint, black oxide, etc.) for my metal working projects. Paint takes a long time to dry, requires multiple coats, decent temps to spray and is not friendly for spraying indoors (and we live in Wisconsin – so this is important for half of the year).

Basic setup L-R, rack for powder coating, oven, powder coat gun in drawer, blast cabinet, dust deputy cyclone

With my recent retirement (yeah!), I was nearing hte completion of redoing my daughter’s kitchen. At this point I was looking to the next few projects (redoing house exterior lights, redoing bridgeport and SBL controls, new exterior path lighting, David’s motorcycle, etc). These would mean either lots of spray painting and future redos or we could get this done with powder coating. For example, I cleaned up and then had professionally powder coated the crash bars/ engine guards for my bike (Honda VTX-1800) which cost $120. Talking with the shop guys at HyTech Powder Coating in Waukesha they said the typical minimum is $80-120 or small projects. While they did a great job, I restarted thinking about a DIY approach and being able to do powder coating as needed.

Powder coating involves:

Mechanically cleaning the part to enable good finish adhesion. This typically means abrasive blasting and chemical wipe.
Electrostatically spraying a paint powder on the part
Baking the coated part to fuse and cure the powder into the final finish

This is basically similar to conventional spray painting. However there are some similarities and differences. :

Prep in either case is key. However Powder Coating does seem to place greater emphasis on mechanical bonding and hence the need for abrasive blasting.
Spraying the finish requires a special gun but this is in the same price range as a decent HVLP spray gun. Masking of areas not to be painted requires either silicone plugs or special tapes due to the high temperatures used in the curing. I picked up the Eastwood dual voltage powder coat gun.
Oven for curing . This can be as small as a toaster oven or a room sized monster used for powder coating car chassis. For the work I will be doing, a home oven is big enough. DO NOT think you can use your regular home food / baking oven for both purposes. Plus you will need additional ventilation for the fumes. Fortunately, used stoves / ovens (esp. wall ovens ) are dirt cheap. You do want a convection oven. Check your local Habitat for Humanity Restore or Craigs List. I got mine at Habitat Restore in Waukesha, WI . A 30″ GE Profile convection oven for $25 (~1% of the original price) . This wall oven did require a basic cabinet in which to reside (which would also get drawers and drawers eventually).
Rack to hold the pieces while spraying. I picked up a stand from Eastwood but it was designed for elves or dwarves and had to raise the top by 3 feet to bring it to a workable height.
Blast cabinet. This was the most costly item both in initial purchase price and parts for modifications. I bought the Harbor Freight 40 lb blast cabinet (with the 20% off coupon). However doing the necessary mods basically doubled the price in added parts. Check youtube for the many videos on souping it up. Must haves: caulk ALL the joints form the inside with Vulkem – it leaks powder like a sieve, metering return line off of the dump chute to feed the blast gun, lowering the grate inside, adding a separate pressure regulator for the gun, additional baffling for air intake and extraction, dust deputy cyclone ahead of the shop vac, new lighting, wheeled caster base, additional outlets for shop vac and powder coat gun, EZ open wing nuts for the window for replacement / maintenance. Yes this sounds like a lot but think of it as a “partial kit” and go from there. Besides my 4yo grandson – Sawyer had a lot of fun helping. Good thing it was all metric as I taught him to grab the 8, 10mm wrenches vs trying with imperial fractional sizes.