Nails as clues to ageBy Mark Chervenka
Nails as clues to age
Most everyone knows that handmade nails are older than machine made nails. But could you identify a handmade nail if you saw one? And could you separate an old nail from a reproduction nail? In addition to looking at how old nails were made, this article will also discuss how to examine nail holes, rust left by nails plus where, how and why specific types and shapes of nails were used.
How nails work
Nails, modern or antique, are able to be used as fasteners because of the cellular structure of wood on the microscopic level. As a nail is driven into wood, the tip of the nail pushes apart or crushes wood cells in its path (Fig. 3-A). When the tip of the nail passes, the cells spring back and try to resume their former positions. This applies pressure to the nail shank (Fig. 3-B) in the opposite direction of the nail path and creates resistance which holds the nail in place. The principle is the same for all nails old or modern regardless of shape or how they were made. Mathematical formulas can accurately predict the holding power of nails based on size of nail, depth nail is driven, and the species and moisture content of the wood.
Nails have been in use since the beginning of the Bronze Age, ca. 1800 B.C. From that time to the beginning of the 19th century, ca. 1790-1810, most nails were made entirely by hand at the forge. A nail cutting machine designed in the 1790s cut the nail's shank and reduced hand labor to only forming the head of the nail. At the time of their introduction, these machine cut nails were sometimes referred to as "cold nails" because they were not made at the forge. These machine/handmade nails were used up to the end of the 19th century. By the 1890s, the entire nail was completely machine formed producing the rounded shank or wire nail that continues in use today.
American hand wrought nails--those made entirely by hand or headed by hand--were done by metal workers specializing in nail-making as well as blacksmiths who made nails part time or to order. The work was hard and gave rise to an early expression, "to work like a nailer" used to describer any intense activity. Most of these nails were formed from a nail rod, a bar of iron available from iron mills close to the approximate size of the nail. Nail rods were at first imported by American nail makers from mills in England but later used bars made in the colonies.
The first step in making a hand forged nail was to form the shank. Next, the head was formed with a heading tool (Figs. 5-B & C). Early nails have two types of heads: a round head whose head is above the surface of the wood and used for general purpose fastening and a T-head whose head is driven below the surface and used for finish work. The forged round head nail is also called a rose head because the hammered head often resembles the petals on a rose. A variation of the T-head, the L-head, is the same as a T-head but with half the head cut off. Cross sections of pre-1800 nails are generally square; shanks from 1800-1890 are rectangular; modern shanks are round.
The earliest forged nails are identified by their irregular shanks and hammer marks on both shanks and heads. When viewed from above, early round heads have a meandering outline that is anything but round. Later machine cut shanks will still show hammering which was necessary to form the head. Fully machine-made nails used since the 1890s have round shanks and round heads like those in Fig. 6. Modern heads in particular are virtually always a nearly perfect circle.
Reproductions of hand made nail shapes are currently being made by casting in a mold. These new cast pieces typically show mold seams and/or grinding marks where the mold seams have been removed. Generally, this means along the shanks and across the heads. Rather than a broadly dimpled hammered surface, cast nails have a very gritty textured surface. Some late 19th century nails were cast but had very limited use. In general, any nail with molds seams or grinding marks should be considered of recent manufacture. Some genuinely old cut nails with hand forged heads may have burrs along the edges of their shanks. These burrs should not be confused with grinding marks that appear in the middle of the shanks and heads.
What you can learn from nail holes
Pieces that have been around for 150+ years frequently have at least a few original nails either missing or replaced. Looking at the holes left by the missing nails can provide valuable information.
The irregular forged heads of early nails, for example, leave an irregular impression in the wood. Perfectly round heads on modern wire nails leave an almost perfect circle impressed in the wood; early finishing T-heads leave a rectangular impression (Figs. 13-15). Irregular impressions from early round headed nails are correct in hidden or unseen places such as backs and sides of drawers, backs of cases, etc., which is where they were originally used. Finding rectangular impressions from early finishing head nails in those same locations is wrong--the small T-headed finishing nails were used in exposed areas. The explanation is often that genuinely old wood that at one time was visible has been used to repair, or entirely replace, the original wood, or that the entire piece is a totally made up. It either case, the types of nail head impressions can be a clue that the piece is, at the least, not original, and at the worst, a deliberate fake.
Pay particular attention to molding, trim and other exterior details. In these positions you should expect to find small T-head finishing nails driven flush with the surface on early furniture. You should not find tiny filled in nail holes which are generally a sign that modern round headless finishing nails have been used.
A few replaced nails are probably honest repairs and can actually enhance a pieces' claim to legitimate and normal wear and help authenticate age. Wholesale replacement or nails mismatched to their original function are a warning sign of potential problems.
Color of the nail hole
The condition of the wood surrounding nail heads and nail holes can provide additional clues about age. Early forged nails are a type of wrought iron with very low amounts of carbon typically about 3 to 4 per cent. This type of iron has a very high resistance to corrosion. That's why wrought iron was used for early architectural features like balcony railings, gates and other pieces meant to be used outdoors. In addition to the low carbon, forged nails are also somewhat protected by the fire scale which forms on the surface as a result of being heated in the fire.
The high resistance to corrosion is due to how low carbon iron oxidizes, or rusts. When exposed, it develops a blackrust (Fe304) that does not flake off. This stable film of rust actually prevents further corrosion by keeping oxygen away from the underlying metal. Red/brown rust, (Fe203) is the more common type of rust that causes serious flaking and damage to iron with higher amounts of carbon. This rust is typical of most new cast iron reproductions.
Knowing how iron corrodes and what colors of rust are formed, helps us tell what types of nails were used even if the original nail is missing. When an early wrought iron nail corrodes, or rusts, it leaves a black stain in the wood around the nail hole. Newer nails made of iron with higher carbon leave red/brown rust stains in the wood. The extent and penetration of discoloration caused by either type of rust depends on the type of wood and where a piece has been used or stored. Some woods, like oak, have very strong natural acids and tend to produce deeply saturated stains.
Be sure that the condition of the nail matches the surrounding wood. It is a common practice for forgers to combine old wood and old hardware--including nails--from several genuinely old derelict pieces to make one "good" piece. If the wood around the nail head is blackened, then the nail should be blackened too. Removing a rusty nail from rust-free wood is a danger signal that should cause immediate suspicion.
You should never base your evaluation of a piece on one piece of evidence alone. The presence of hand forged nails is not a guarantee of age by itself. Analyzing nails, nail holes and the type of nails used in various locations is just one step in gathering information upon which to base your decision of age and condition. Early forged nails salvaged from old pieces and modern reproductions shaped like early nails are easily obtained. A healthy skepticism is your best defense against a fake. And ALWAYS ask permission before you conduct your inspection.
Nailhead impression & nail holes