Introduction: Christian 'Ichthus' (Fish) Auto Bumper Emblem

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first to…

Even my local auto parts store has a Christian fish emblem made of chromed plastic. Why would anyone make his own rather than simply buy one for a few dollars and stick it onto his bumper?

I want one that includes the Greek letters spelling the word 'ichthus' (Greek for 'fish')* inside the body of the fish outline. I had one of these on my car, but I sold that car and now drive a different car. Once these emblems were very easy to find in stores, but they have disappeared. They are not to be found on the Internet, nor in catalogs. I will make my own. What I present here could serve for someone who needs this emblem or another of his own choosing. Some Instructables members who regularly make jewelry may have better tools and processes than those I am using.

*In a later step I will explain the meaning, history, and use of the 'ichthus' (fish) symbol in earlier centuries.

Step 1: Tools and Materials

  • Sheet aluminum about 14 gauge
  • Double stick foam Scotch Mounting Squares
  • White paper (one sheet)
  • Aerosol clear coat in a can
  • Coping saw
  • Draftsman's compass with inking pen and fountain pen ink (or India ink)
  • Marker pen
  • Drill and bit
  • Exacto knife
  • Pocket knife
  • Various files
  • Sandpaper
  • Vise with soft jaws

I chose to make my fish emblem from sheet aluminum because its color will not change much with age and weathering. The other significant material is some Scotch Mounting Squares or Tape. It will be used to attach the emblem to the car.

The tools are a drill to make openings for cutting internal parts with a coping saw and a file. A draftsman's compass will be used in the pattern layout. An Exacto knife will be used to trim away non-essentials from the pattern so it can be transferred to the aluminum. A pocket knife is useful for trimming away excess material on the aluminum. Some sandpaper or emery cloth is good for smoothing edges in tight places.

The aluminum measures 0.062 inch thick, or about 14 gauge. It is from the front shroud on a household furnace. I found it at a local scrapyard. Another option would have been to make the emblem from steel rod bent and welded together. Then I could have applied braze material to provide finish like brass. But, an emblem made of steel would also be heavier and more difficult to keep on the car without falling off.

The blade on the coping saw is a very ordinary blade. A quick test showed it will cut my aluminum very well. I will hold the aluminum in a vise while working.

Step 2: Pattern Layout

The basic Christian Fish Symbol is two arcs laid over one another. I wanted a certain desired proportion between the length and the height of the fish body.

I made a straight line down the center of a piece of paper. Then I scribed an arc at a radius of 3 1/4 inches. I scribed another from the other side. Then I used the same centers for the arcs, but set the radius to 3 inches. The height of the fish's body from top to bottom is 2 1/6 inches. That eventually yielded a fish symbol 5 7/16 inches long. To my eye, this looks about right.

Step 3: Inking the Pattern

I have a full set of POST drawing instruments. I removed the pencil lead holder from the compass and substituted the inking pen. The first photo shows this relatively close-up. Normally these use India ink. I had only fountain pen ink. I adjusted the points and dipped the end in the ink. I checked the flow on some scrap paper to get it the way I wanted it. Then I scribed over the pencil arcs. See the second photo. Later I used White Out to clean up the tail end of the body so the crossover lines will not confuse me when I actually use the pattern. At this point, all pencil lines may be erased.

I held a straightedge across the paper at the top and bottom of the fish body. I determined the ends of the fish's tail would be where the straightedge intersected with the arc lines.

Now people would probably use a CAD program to do all of this. I feel more confident with my drawing instruments.

Step 4: The Letters

The next step is to add the word 'ichthus' with Greek letters. I began with the middle letter and worked out the spacing toward both ends. (I could have turned the outline of the fish over and could have begun from the head rather than from the tail. If I wish, I could still flip the pattern end for end during the process of transferring it to the aluminum sheet to make the lettering begin at the head rather than the tail.)

If you want to look at the letters from a printed chart of the Greek alphabet, the letters in order are: iota, chi, theta, upsilon, and (final) sigma.* As shown, they are the lower case version. If you chose to make the letters upper case, click on the second photo to see both the lower case and the upper case version. The letters in the second photo were made in Writer using BST Greek fonts downloaded free to make a corresponding on-line Bible program display properly. The final sigma at the end of the lower case version came from the Character Map inside Windows Accessories.

I drew these letters freehand in pencil and then went over them with a black gel pen. I would have used a fountain pen, but there is less probability of smears with a gel pen. Some smoothing can take place by finishing the lines with a file after the pattern has been transferred to the aluminum.

I have included my pattern in PDF for anyone who wishes to use it, perhaps with a computer driven plasma cutter.

The Greek word 'ichthus' means "fish." Even today, someone who studies fish is an ichthyologist. (Early Christians adopted it as an acronym for "Jesus Christ, God's Son, Savior" (iesus xristos theou [h]weos soter). Allegedly, when a Christian met someone on the street and wanted to give a recognition symbol or begin a conversation and be assured the other person was not someone who would turn him in for persecution by authorities, he would make an arc in the dust with his foot. If the other person was a Christian, too, he would make a second arc to form a fish.

*The letter sigma has one form if used at the beginning or inside a word and another form if used at the end of a word. Greek fonts in a typical word processor provide the internal sigma, but not the final sigma. The Windows Character Map usually includes the final sigma. Also, some font schemes represent the sigma, both final and internal, with the letter "C".

Step 5: Cut the Pattern Out

I made a photo-copy of the pattern as it was this far just to have a backup in case anything goes wrong. Then I used an Exacto knife to trim away everything on one of the copies that does not belong. Some distortion is certain to be introduced.

Step 6: Copy the Pattern to the Aluminum

I carefully held the pattern in place with one hand while tracing around the pattern with a marker pen.

Step 7: Cut the Sheet Aluminum

There are a variety of ways the emblem can be cut from the sheet aluminum. I chose to use my coping saw. My blade is really a wood cutting blade with only 15 teeth per inch. Blades with as many as 28 teeth per inch are available for cutting metal, but I am using what I have. I support the work on the jaws of my bench vise opened about 1/2 inch. That is not visible in the photo. I also put some soft jaws of flattened PVC into my vise and used them to hold my emblem while I was working.

15 teeth per inch on my blade made it difficult to control the saw cuts properly, and I made a couple of unwanted nicks in my emblem. They are more disappointing than damaging, but I may fill them with an aluminum solder from Bernz that I got a few years ago at Home Depot. I have also learned my coping saw cuts aluminum quite well with more control when I drag the blade contrary to the set of the sawteeth, rather than pushing the sawteeth into the work. Had I realized that earlier, I would not have made the nicks. 

When I get to a corner where I need to turn the blade, I drill a hole so I can make the turn easily.

(I have had this coping saw since I was a small boy. I lost the outer blade retainer and made a replacement from a 5/16 inch hex head bolt about 1/2 or 3/4 inch long.)

I am trying to stay a bit wide of the line, but it is very easy to cross the cut line with a poorly executed stroke of the saw. I plan on filing to finish.

Step 8: Drill Holes and Begin Removing Material

I have drilled holes in all of the areas to be removed. The area between the chi and the theta has already been removed. Because it is so small and narrow, it is the most difficult area to remove. The red rectangle in the photo is a piece I cut from a belt from my belt sander after it separated at its joint. Thin strips from an old sanding belt make a nice tool for smoothing edges where space is limited. I could use a set of needle files, but I do not have needle files. The holes are large enough to pass the end of a coping saw blade, even though the pin may need to be pushed aside a little so it can pass through the hole. One pin did fall out. I found a small wire brad and am using it as a blade pin, now.

As I cut out areas to be removed, I find I sometimes need to trim away a little more material. I pare at the aluminum with a small blade on a pocket knife. That is usually effective.

Step 9: Prepare to Attach the Adhesive Foam

When finished cutting out areas to be removed, smooth the edges of the emblem and remove any burrs. Polish the good side with steel wool or fine sandpaper, or buff with a wire wheel. Spray the good side with aerosol clear paint and allow to dry thoroughly.

Select a place on the car where the emblem will be mounted. Hold the emblem on the car as it will be when mounted. By hand gently bend the emblem to fit the contours of the car's body. I looked for a place that is as flat as possible.

I pulled the protective covers from one side of three mounting squares and attached them to the back side of the emblem.

Step 10: Trim the Foam

Use an Exacto knife to remove the areas of foam that are visible peaking out from under the aluminum on the emblem. Look for little pieces of foam that have balled up.

Step 11: Mount

Clean the surface of the car's body from dust and moisture. Remove the adhesive backing. Align the emblem as much as possible exactly where you want it to be. Gently allow it to make contact with the car's body. Once it is in place, you will not be able to move it.

Perhaps the reason the 'ichthus' fish symbol disappeared from the market is that fewer people know what it is and what it means. But, if that is the case, it can be useful, too. At sometime someone will surely ask what it is and what it means. That is a ready opportunity to explain what it means and why Christians use it.