Video
Iron Fence Repair
Transcript
Hello, in this video we're going to discuss the basic procedures for preserving historic iron fencing. Two things to keep in mind are the first, do no harm to the artifact itself, and secondly always exercise personal safety. The first step before beginning any restoration project is documentation. It is important to document the fence as you found it before any work begins. This may be done by filling out a survey form or just writing a narrative description of the fences condition. It is also a good idea to take lots of before, during, and after pictures of the project. Keep in mind, to take pictures of both the details and the overall area. One detail to keep in mind when documenting your fence is to look carefully on the ironwork for any remnants of the original or older paint. On a heavily weathered fence, these may be found underneath the rails or where parts connect. Generally, we think of fences as painted black, but historically a fence could have been painted a variety of colors such as: green, white, or even have a metallic plating. If any remnants of the older paint is left, this should be photographed and included in the documentation. This may also help you decide what color to paint the fence. While we are writing our documentation, let us discuss ways to distinguish between cast and wrought iron. Cast iron is made by heating iron to a fluid state and then pouring into a mold. It is fabricated in sections that are then bolted together. Cast iron is heavier and cheaper to make. The molds allow for more intricate detail, however. Wrought iron is iron drawn and worked slowly with continual heat and pressure. Since it is shaped by forging, this allows for simpler more delicate pieces and is lighter than cast iron. The pieces are put together with rivets or fused together. The fence that we would be working on this video is a wrought iron fence that has cast iron corner posts. Now that we have documented the project, the next step is to always cover up any objects in the area where the work will place. It's particularly important to cover any stone grave markers as well as any stone or masonry curbing that may be under the ironwork. Rust, chemicals, and the paint will all cause damage to this stone. Another important thing to check on the fence is that the bottoms of the iron panels are free from the ground. Only the corner posts and support brackets should be in direct contact with the soil. Any unnecessary ground contact will cause the iron to corrode. If the fence panels are in contact with a ground they may need to be raised or most likely the soil should be dug out from underneath them. Now that you've been paying particular attention to the fence you may have noticed loose disconnected or broken connections. It is important to fix these so the fence will be properly supported. Tighten all those bolts first. This may require the additional use of a lubricant. If any bolts are missing, these will need to be replaced at this time. Uou may want to remove one of the original bolts to match the size and style for the replacement. Iron bolt is the best replacement. Stainless steel may also be used. Occasionally bolts are broken off or rusted in the brackets. These will need to be carefully drilled out and the holes reach out to its original size if possible. It is important to center punch the hole and use a drill bit smaller than the original hole. Okay, let's get started checking to see if the fence panels and posts are straight and level. If they are not you may want to lift or lower the corner post. This is only important if the panels are so far out of alignment that they are not fitting together correctly. In some cases posts may be set in stone or concrete. If the base of the post is too heavy or large to the ground then it should be left alone. Otherwise the base of the post will need to be exposed and lifted to the desired height. Gravel or dirt can be placed under the base to stabilize it at the needed level. The next order of your project is to check if any of the wrought iron parts are bent or damaged. If there are any bent elements on your fence, these can be easily straightened with little effort and the right tools. Now that we have addressed all of our structural issues let's work towards stabilizing the iron. We want to remove only the loose powdery oxidation and any rust scale that is on the surface. Keep in mind that we're going to treat this fence with a rust converter. So, some rust must remain. To do this, we're going to use a stainless steel fine wire brush. Heavily corded or twisted wire brushes are too aggressive for historic iron work and can easily remove too much material. When selecting a wire brush, you want to choose a finer wire. The fine wire lasts longer and is more flexible to reach tough spots and corners. I do not recommend sandblasting since some of the fences detail could be lost and the iron will get over cleaned. Once the surface has been wire brushed, you will need to remove all the loose rust and dirt. Washing the surface with a solvent or non ionic detergent. They can be mixed with solvent will clean and prepare the surface for painting. This wash will also remove any oil left behind around the bolts. After the surface is completely dried of all moisture, we then treat it with a rust converter. Keep in mind this is a rust converter not a rust inhibitor or rust dissolver but a converter. A converter works by chemically changing the iron oxide into a more stable iron tannate or iron phosphate. Most commercially available rust converters are phosphoric acid or tannic acid base. Some are even a combination of the two. The only word of warning, if using a phosphoric acid based converter, is that moisture, including high humidity, cannot come in contact with the surface until a treatment is completely cured. If affected by moisture the surface will turn a chalky white and must be recleaned. Keep in mind that when using any chemical to follow the manufacturer's recommendations for safety and personal protective equipment.
The rust converter must be brushed or sprayed on all surfaces of the iron, paying attention to coat any under surfaces and crevices. Use extreme caution if spraying the converter because any contact with stone will cause an irreversible black staining. Once all iron surfaces have been treated with the rust converter, it must have adequate time to cure before you can move forward with the restoration. Check the manufacturer's label for the curing time of the converter that you were using. Once your surface has dried and the converter has had time to properly cure you can begin priming the fence. You want to choose an oil-based primer that is specifically designed for use with metal. Some primers have rust preventative additives. These are good but not necessary since you already used a rust converter. One or two coats may be needed depending on the coverage. You want a nice even coating that is free of any gaps. It is recommended that all primer and paint be applied by brush to prevent over spraying and staining in the cemetery. Now that your primer has had time to dry we can begin our topcoat. The color that you choose to paint the fence is your own choice that may it be affected by the fences original color or colors commonly used when the fence was originally installed. You may need to consult local ordinances to see if there are any color restrictions in your cemetery. When choosing paint you want an oil-based paint designed specifically for the use with meta. Two coats of paint are preferable to get a good solid surface coating.
Now that you've watched this video hopefully you have all the basics you need to preserve your historic iron fence. One thing to keep in mind, if your fence is heavily damaged or corroded is to consult a professional conservator and always remember to exercise personal safety and to do no harm to the object itself and good luck.
Description
Materials Conservator Jason Church demonstrates how to properly repair an iron fence. A Spanish language version of this video is planned.
Duration
9 minutes, 2 seconds
Credit
NCPTT
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