Tips and Techniques for Soldering Copper - February 2020

Fri, Mar 13, 2020

Joe Jenkins, Traditional Roofing Magazine 

Make Your Seams Tight and Clean

Clean and tight seams are essential; solder much prefers bright copper with a very close fit. Lap seams should have a minimum one-inch overlap and no gaps larger than 1/16-inch. Install only as much copper as can be soldered by the end of the day. Sloppy or dirty seams take much longer to solder; the extra time spent making a clean seam will pay dividends when soldering. Figure 1 shows what a good lap seam looks like, Figure 2 shows a good flat-lock seam. 

copperRiveting Made Easier

Carry self-drilling, metal lath, pan-head screws, size 8, about 1/2-inch long in pouches or rivet boxes. These will hold the sheet or panel in place, can be easily removed, drill exactly the correct size hole for standard rivets and can be reused indefinitely. Install the screws along the entire length of a lap seam working from the bottom to the top, then remove each one and replace with a rivet. You won’t get copper shavings stuck between the sheets since they’re held tightly together. 

Peen Down Joints

Even the best seams always have some gaps, slightly protruding rivet heads or irregularities that require extra attention. Use the well mushroomed head of a wide brick set to gently tap lap seams and rivet heads flat, taking care not to dent the joint. The wide blade of the brick set is handy for getting corners of box gutters tight. Go over flat-lock seams first with a Nupla four
pound dead blow hammer and then again with a two-to-three pound drilling hammer with a slightly convex face, hammering the leading edge of the overlying panel flush with the adjacent panel. This allows the soldering
iron tip to more easily bridge the flat-lock seam.

Flux It

Purchase some Stay-Clean Liquid Flux by Harris. Don’t dip your brush into the quart container or you’ll dirty the whole quart. Pour a half-finger at a time into a small glass container (baby food jars are great) and work from that. You can find Harris Stay-Clean at a good welding supply store.

copper 2Make Sure the Iron is Hot

Good soldering is done with the solder flowing in the liquid stage, not the plastic stage. The solder should look like you’ve laid a ribbon of liquid mercury on the copper (see Figure 3). If you’re getting ridges in the finished solder, turn up your iron and slow down.

Keep Solder Clean

Solder bars are a bit like welding electrodes: they like to be kept clean and dry. If you let the solder roll around in your truck or gang box, you’ll get impurities on the bars which will accumulate on your iron tip and require difficult cleaning.

Dip Your Tip

Here’s how to prepare a good iron dip: combine three parts tap water with one part Ruby Fluid in a medium sized glass jar with a tight-fitting lid. Quickly dip your hot soldering iron tip in this mixture after soldering each joint and watch the dross come right off, leaving the tip clean and bright. No more brushing or wiping or cleaning with sal ammoniac (Sal ammoniac is a naturally occurring mineral composed of the salt ammonium chloride. The name “ammonia” actually derives from the name of this mineral, having been known since antiquity. It can be purchased in hardware stores and often times in grocery stores in the spice aisle.) It’s also useful for cooling down your iron if it gets too hot. Figure 4 shows iron dip and flux jars.

copper 3Use an Electric Iron for Vertical Joints

Use a 550-watt American Beauty soldering iron with a chisel tip for soldering your vertical joints. Hold the iron perpendicularly to the joint, press the tip into the seam and work from top to bottom. The joint can be soldered beautifully in one pass. The vertical joint in Figure 5 was soldered with an electric iron. Since these irons are engineered for shop work, they don’t get hot enough in ambient temperatures below 65ºF and, under those conditions, you may want to revert to propane fired irons.

Use Iron Correctly

Both lap and flat-lock seams should be soldered in one pass with the hot iron placed across the joint so that the most heavily massed part of the tip is on the folded or “high” side of the seam. Remember the heat is transmitted from the soldering iron tip to the seam through the puddle of molten solder bridging the joint so, as in welding, watch your puddle and work continuously.
copper 4

Wash Joints

If joints are not washed properly after soldering, the flux remains active and will leave a green discoloration on the adjacent copper. Keep a pump sprayer filled with tap water and a few squirts of dish soap. Spray joints and adjacent copper copiously and scrub thoroughly. This works quite a bit better than the usual baking soda and water scrub. The sprayer acts as an emergency fire extinguisher as well. The sprayer and soldering outfit are shown in Figure 6.

FRM

All photos by Christopher Paulin, Paulin Slate & Copper. Reprint permission from Traditional Roofing Magazine, a division of Joe Jenkins, Inc.
copper 5


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