Upholstery Repair ( damaged tack edge )

A recurring problem in the repair of upholstered furniture is the degradation of the edges where the upholstery is tacked to the piece. Many upholsterers are not wood workers, so when removing old upholstery you never know what you will find. The picture below is of an Eastlake chair that has been recovered so many times that there is little left to drive tacks in to. You can see that the last man to upholster this chair drove tacks into the face of the rail in order to attach the fabric. I have seen all kinds of attempts to repair this type of damage, every thing from nailing wood to the frame to Bondo auto body filler.

damaged chair edge

The first and most difficult task is to remove all the old tacks in the edge of the rails. Most upholsterers will just leave many of the old and broken tacks in place. The remnant tacks will damage your edge tools when repairing the edge of the rail.

edge routed

A rabbet is cut into the edge of the rail with a router plane and chisels.

edge replaced

Replacement wood glued into the rabbet.

ready for upholstery

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Expantion Rates and Wood Movement

All materials expand and contract due to heat, and in some cases moisture, and in some cases both. Each material expands and contracts at different rates. Different metals expand at different rates due to heat, as the metal warms up the molecules move apart and as it cools they contract. Wood primarily expands as it absorbs moisture and contracts as it dries out. Different woods expand and contract at different rates.

The amount of expansion in relation to the amount of heat or moisture is called the coefficient of expansion.

When we build objects we need to take this expansion and contraction in to account, we primarily think about wood movement but in some cases we must also be aware of the movement of metal. Wood glued directly to metal always fails eventually, because of the difference in expansion rates, it doesn’t matter what glue you use. Even a flexible glue like construction adhesive will eventually fail due to repeated expansion cycles, it’s like bending a piece of wire back and forth until it breaks. Even if there was a glue that would not fail the difference in expansion rates would cause the object to warp and deform. When laminating metal to wood one must allow for movement. We must also consider the effects of compression set. If you are not familiar with compression set it is explained here.

Below are several tools made of brass and wood.

                            Here is what happens when wood is glued directly to metal.

Notice the piece of brass that is proud of the wood.

The brass is dovetailed into the wood allowing for movement.

Mechanically attached to the wood.

Compression set.

Fastened in the center allowing  movement

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Finish Adhesion Failure

There are two places where a finish can fail to adhere. The finish can fail to stick to the substrate (substrate adhesion) or it can fail to adhere to the previous coat in the finishing system (inter-coat adhesion). There are two types of adhesion that affect a finishes ability to stick to a surface: mechanical adhesion and chemical adhesion. Mechanical adhesion to the substrate is affected by how you prepare the surface, sanding or planing. A surface can be too finely sanded or too smooth for some finishes. Inter-coat adhesion is affected by scuff sanding between coats or the ability of some finishes to burn in to themselves or chemically bond. Both types can be affected by contamination.

In my experience most adhesion problems occur with the modern finishes, polyurethanes, waterbornes or two part finishes. Adhesion failures with shellac, lacquers or traditional varnishes seem very rare. Problems when mixing waterborne and solvent borne products in the same schedule are common.

Here is a partial list of causes for adhesion failure in no particular order.

  • Excessive substrate moisture content
  • Improper sanding procedures- polish sanding substrate
  • Incompatible coatings within the finishing system
  • Insufficient curing and dry times.
  • Contamination of substrate
  • Extreme temperatures
  • Excessive pigment load in stains
  • Omitting scuff sanding between coats with certain finishes
  • Natural oils and resins in teak, pine, etc.                                                                                                                                                                                                                                             Below are two pictures of a desk, it was over coated with a polyurethane varnish in an attempt to spruce it up. With out adequate mechanical adhesion, I was able to remove the entire top coat with a single edge razor blade.

This is a rocking chair that someone stained with a heavy coat of oil based stain and then top coated with a water borne varnish, then I got to work on it.Same rocker. It was stripped and refinished with lacquer based products.

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Thoughts on Design [ A Short Introduction ]

Design

“Too often professional insecurities are masked in impenetrable language and professional reputations are buttressed with unnecessary complication, and confusion.” David Savage

In 1965 I enrolled in college and started a program of study in architecture. As one of the requirements of the architecture program I took a sketching class, the purpose was to learn to draw the trees around the buildings I would design. I also took my first design class that first semester. One thing led to another and before I knew what happened I was an art major. After three semesters I took a short vacation in south east Asia, when I returned I went back to school and continued to study art and design. I eventually finished college and got a job teaching art and design. First let me tell you that I’m not writing this to brag about my college experience, what I’m trying to say is that I graduated from a respected University with an MFA in art and design and didn’t have a clue about how to teach or explain design to anybody, I knew all the vocabulary, I had read all the books I could talk design with the best of them, but I knew something was missing, it didn’t all make sense, it didn’t all fit together, I was still confused.

Studying design is one of the most confusing and frustrating things one can ever attempt to do. All you have to do is read the Wikipedia page on design and try to use what you read to design a piece of furniture, or any thing else. One of the problems is that all the words used to discuss design have multiple meanings and the word design itself has multiple meanings. The on line dictionary lists seventeen definitions for the word, both noun and verb. Design can be a process or it can be the results of the process. Sorting out and making sense of all the written material on design can be a daunting task to say the least. Much of the material is not only confusing it is down right contradictory. Much that is written on design is based on philosophy and if you don’t share that philosophy it’s not helpful. For example the statement “Form follows Function“, this is a statement of a philosophy of design and if you don’t embrace it, it won’t help you design anything, however that statement is one of the founding principles of 20th century design.

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Well I got lucky, one Friday after work, while sitting in a tavern drinking beer with a bunch of art teachers I mentioned that I was about to teach a beginning design class and had no idea what to do. I asked did any body have a Design I syllabus? There was an old gentleman sitting there that had studied at the Art Institute of Chicago in the forties. In a couple of hours in that saloon he taught me a structure, a way of thinking about design that tied it all together. A way to simplify design.

All the confusion was not necessary, There is a simple explanation and process that allows us to understand good design. There is a set of elements and principles that explain good design from all periods and within all philosophies and cultures. In design at least I think there is a theory of every thing. The theory is not a formula or cook book for creating good designs but a way to analyze and study a good design. If we can understand what makes one design more successful than another, it may help us improve our own designs.

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In the previous paragraph I repeatedly used the term “good design”, I’m not sure good design really exists. I think there are more successful designs and less successful designs. Albert Sack said Good, Better, Best.

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Design is not period specific. The elements and principles of visual design are based on how we see and how our brain interprets what we see, not when we see. The elements and principles apply to all periods. These elements and principles can be used to discuss and analyze any piece from any period. In furniture design there are archetypes that do not change. If you are going to sit on a chair your legs need to fit under the table during any period, if you are going to sit on the floor the table needs to be lower. What does change is culture, engineering and style. An example of change in engineering is drawer construction, during the William and Mary period drawers were often nailed together, during the Chippendale period dovetails were used. The high versus low table is a cultural change. While culture modifies how we interpret what we see the elements and principles still apply.

What is Design?

Design is the organization and manipulation of the elements of design through the principles of design to achieve an out come. That’s it, it’s that simple, you have elements, principles and outcomes.

The Elements of Visual Design: There are three primary elements and one secondary element of visual design. The primary elements are line, value and color. The secondary element is texture. These are the elements of visual design because these are the basic building blocks of what and how we see. Not only are these the basic building blocks of what we see they are the basic building blocks of what we design.

The Principles of Design: There are four principles of visual design. They are repetition, variation, opposition, and transition. These principles are what happens to or what can be done to the elements. Any visual element can be repeated, it can be varied, it can be opposed or it can be in transition.

Outcomes: When we design we use the principles to manipulate the elements to create a result or outcome. This is what visual design is at it’s basic level. Form, balance, proportion, motif, shape and all the other similar concepts related to design are all results or outcomes of the design process.

Texture: Texture is a special case. Texture can be the result of the repetition of an element so in that respect it is an outcome, but at the same time it can be manipulated by the principles as an element.

 Time: Time is another special case, time is neither an element or a principle but it needs to be considered in the design process. It can be used as an element, Alexander Calder used time as an element when he built his mobiles. The mobiles moved so they had to work at any moment in time both visually and in their engineering. When we walk around a piece of furniture it’s engineering does not change but it changes visually from moment to moment as we move so time effects the visual design.

Repetition with Variation: Repetition and variation are the two most important principles. It is repetition that unifies a design and ties it together, it is repetition with variation that adds interest. The human mind is always subconsciously trying to make sense of and create order in our environment. Our minds are always searching for likeness, looking for the same color, looking for the same shape. We are constantly subconsciously putting thing in groups, it’s one of the ways to make what we see simpler.

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When ever we build a piece of furniture or anything for that matter, unless we are copying someone else’s design we are designing. If you create an object it is designed. The question is not is it a good design or bad design. The question is does this piece achieve our intended outcome, if yes, why? if no, why not? There is no formula that leads to “good design”, but there is a way to analyze a design after the fact. In future posts I plan to use these ideas to discuss different pieces and hopefully make more sense of this post.




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Straightening a Warp [ Compression Set ]

One of the most common questions I receive is “can you remove the warp from this_____” fill in the blank with something like table leaves, drawer bottom, or table top. The answer is always the same. ” That depends”.  Anything can be fixed if you are willing to spend enough money. However sometimes it’s just not worth the effort and it’s just easier to replace the part or the whole piece.

In this post I’m going to talk about a method of straightening a warped board, it doesn’t always work, but many times it does. If you are going to try this don’t start right out with your dinning room table or your grandmothers antique desk, practice on scrap boards until you have had some success, this is not as easy as it may appear in this post.

BACKGROUND

Wood is made up of cells that are many times longer than they are wide. The vast majority of the long cells run parallel to the center of the tree. These cells are hollow. Imagining the wood as a bundle of straws is a common way to illustrate the structure of wood. However you must imagine the straws with closed ends and varying length to be a little more accurate.

straw analogy

When the wood is in the tree it contains two kind of water , free water, the water in the hollow part of the straw and bound water the water that is locked in the walls of the cell. Wood in the tree can contain as much as 75% or more water by weight depending on the species and the time of the year. When the wood is cut from the tree, first the free water begins to evaporate, when all the free water is gone but none of the bound water, the wood is at the fiber saturation point, it will be around 30% moisture depending on the species. As the wood continues to season it begins to lose bound water until it is in equilibrium with the relative humidity of where it is located. As the bound water evaporates the cell walls begin to shrink and continue until the wood stops losing water. As the cell walls shrink, the over all dimensions of the wood shrinks. If the relative humidity where the wood is located goes up the cell walls begin to absorb moisture again and begin to swell, as the cell walls swell the over all dimensions of the wood increases. This is what we call seasonal wood movement and it will take place when ever the relative humidity changes, it never stops, ever, finishes will slow it down but not stop it. If one side of a board is exposed to more moisture than the other side, the wet side will expand more than the other side and cause the board to warp or cup. If the cells cork screw through the board as they expand and contract the board will twist and untwist.

Now I know you are saying if this is true why doesn’t a cupped or warped board flatten back out. The answer is compression set. When a piece of wood is confined and it absorbs moisture it tries to expand but can’t, when it can’t expand the force crushes some of the cells, with the cells crushed it can no longer expand and contract fully, keeping it warped or compressed. Compression set takes place whenever the wood tries to expand and is restricted. It also takes place when one side of a board tries to expand and the other side does not. This is normally caused by uneven moisture exposure. Compression set also explains why joints loosen over time. It is the explanation of most cracks, loose screws, loose nails any thing that restricts the movement of the wood can cause it.

When wood tries to shrink from loosing moisture while it is restricted it will crack, check or split at the weakest point. It will split many times where it was punctured with a peg, nail or screw. A wide plain sawed board will split most often in line or near the cathedral grain.

A warped board may be caused by other issues like reaction wood, but most warping is caused by moisture or heat and compression set.

A METHOD OF REPAIR

Common knowledge says to straighten out a warped board we need to apply moisture to the concave side of the board, and if enough moisture and heat are applied to the concave side, the board will temporarily straighten out. However as soon as the introduced moisture dries out the board will go right back to the warped position or may even warp more if the process causes increased compression set.

The best chance of removing a warp is to introduce a compression set to the convex side of the board by introducing moisture to the convex side while the board is restrained from moving. This can be very time consuming and difficult if the warp is severe.

A technique I have used with some success with small tops and drawer bottoms is, 1. clamp the board straight with clamps and heavy aluminum angle irons so it is unable to move. 2. Lay the piece on the damp grass with the concave side up for a period of time, the length of time depends on how sever the warp is. 3. Leave the piece in the clamps in the shop until it is in moisture equilibrium. 4. Repeat until it is straight. A similar process can be done with steam, or even damp blotters.

Here is the carcass of an Arts and Crafts stand up desk.

This is the warped lift top of the desk, it’s only warped on one end.

Here I have wet the convex side of the warped end.

The wet end has been covered with wax paper to allow the water to soak in rather than evaporate. It was then put in the sun with the concave side up for several hours. Only the warped end was in the grass the other end was on dry concrete. The second day it went back on the grass the same way but it was turned over every two hours all day.

It then went back into the shop for several days until it was in equilibrium. I used a moisture meter to compare the top to the rest of the desk when they matched I took off the clamps.

Clamps removed, it’s not perfect but it’s much better than it was.

The top of this candle stand was straightened using  this method. I forgot to take a before picture, you’ll have to trust me, it was quite warped.

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Context [ Ways of Working ]

There is a piece of furniture in your minds eye, but you can’t seem to ever get it out. You can see it in your head as plain as day, then you build it, you step back, you look and it’s nothing like what you saw in your mind. If this sounds familiar to you, here’s why. When you visualize a piece in your mind, you don’t see it in a surrounding, you don’t see it against the wall and you don’t see it on the brown carpet. Even if you try to imagine it in context it’s still an imagined context. When you build a piece that you have imagined, most of the time it will fall short of your expectations. Even if you have drawings or pictures the same thing can happen because the full size reality in context will not match what you saw in the drawing or the photo. Again you are seeing it in a new context. A piece you have already built will look different if you move it into different room, It will look different under florescent light and again different under incandescent light.

Here’s an example of context. Sit back from your screen a few feet and stare at the picture below. Do the two orange dots look the same or does one look darker than the other.

context

They are both the same.

So how does one deal with this? There is only one way, you must let go of your preconceived vision of your work and be willing to make changes and adjustments along the way. When you work directly it’s more like having a conversation with the work, the work tells you what to do next or what must be changed. If you continue the conversation the piece will tell you when it is done it will eventually look finished. Some people build full sized cardboard mockups to work out a design, others make full sized versions in cheap stock over and over until they get it right for the same reason.

Not long ago I was able to spend several unsupervised hours in Frank Loyd Wright’s Taliesin. The house is furnished with a number of pieces of furniture that are made from lumber yard pine and AC plywood nailed together. These pieces are obviously mockups for pieces that were made later in fine woods, they are three dimensional thinking. In this link, the bench in the foreground is one of these pieces, the only one I could find on line. There are several small tables in the living room made this way. I find it interesting that he put the mockups in his own home.

If you are reading this and thinking he’s nuts consider this, Krenov, Maloof and Nakashima all worked directly in some way, and have you ever seen a measured drawing that predates the industrial revolution.
The artist Jim Dine did enough versions of a piece called “Nancy Outside in July” to fill an entire book.

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Wedged Dovetails

If you read Chris Schwarz’s blog at Popular Woodworking, there was recently an interesting post about wedged dovetails. Historically it’s been said that wedging was done primarily to close up gappy or sloppy dovetails. In the coments of that post a gentleman made a case for wedged dovtails as a normal way of construction used by Germanic woodworkers in the past. I would like to agree with this contention for the most part. I would like to re post the comment here but I don’t know if that is allowable so here is the link again. It’s well worth the read, for those that are not familiar with wedged dovetails here are some pictures and comments.

This is a drawer out of a vernacular table that either originated in Wisconsin between 1850 and 1880 or was brought here during that period. The table is solid cherry, the drawer is a  box with a 1/4 inch cherry panel glued to the front. The box appears to be poplar with a pine bottom.

Here is a better view of the cherry panel glued to the drawer box.

Here we see a wedge in the top of each pin. All 12 pins are wedged, note that the wedges are not in the center of the pins, but they are in the interior of the pin not next to them. It would seem that if they were just to fill a gap there wouldn’t be one in every pin, just where there was a gap.

The wedges from the side of the drawer. There doesn’t seem to be a saw kerf that the wedges were driven into. I think that each pin was quickly split with a chisel by eye after the box was assembled, and the wedge driven into the split and then trimmed.

On the drawer front it appears that the drawer side was nicked with the chisel when the pins were split.

Posted in Tables, Uncategorized, Wood Working | Tagged , , , | 13 Comments

Finish Reamalgamation [ just one advantage of shellac ]

This is a Victorian dresser that came in to be restored, luckily it had it’s original shellac finish so it could be repaired and not refinished. One of the advantages of shellac and lacquer is that they can be re-amalgamated.

The first thing I did was to very lightly scrape the top with a card scraper to remove any loose finish and big chunks of debris.

There was a large chip missing from the back corner of the top.

I planed the corner in preparation for a patch.

The patch glued in place.

The patch shaped and sanded.

The top had black water and iron stains.

The stains were bleached and scrubbed with oxalic acid. Actually what’s in the jar is oxalic acid based deck wash.

The top after bleaching and washing with TSP.

Next what remained of the finish was re-amalgamated with denatured alcohol. Basically the old shellac is dissolved with the alcohol and a brush and then brushed out to cover the surface. You are covering the entire top with what finish is left. On a piece with less severe damage this can be done without the need for further repair.

The entire top re-amalgamated.

A coat of toner to bring back the color.

The top polished.

Finished.

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What is Finishing really? [ how much protection do you really need ]

Ask wood workers why we put a finish on our projects and the answer most often given is ” to protect the wood”. This is understandable we put many, many hours in to a project and we want it to last. But how much protection do you really get from the different finishes. Is there a real difference between them? Do this experiment. Take a board any board, divide it into as many sections as you like. Finish each section with several coats of a different finish of your choice. Now find a four year old and sit him or her in front of you finished board with a magic marker, then give the child a ball point pen, then a knitting needle and then a rock, you get the idea. I don’t care what finishes you chose to use, when the child is done you will see very little difference in any section of the board. The truth is that the difference in protective ability of the commonly available finishing product is negligible or only slight at best. I have seen a kitchen finished with conversion varnish all beat to hell in two years and a cherry kitchen finished with just oil that is beautiful after fifteen years.

So what is finishing? It’s a fashion statement, it’s a way to enhance the way a piece looks, it’s a way to make a piece blend in with a decor.

The most important choice in finishing is “how does it look” and next is ” can it be repaired”. If it can’t be easily be repaired it increases the odds of it ending in the trash.

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You Are The Jig

I was reading one of the forums today and saw a post that said a flat back on a parring chisel is absolutely necessary in order to pare without the chisel digging into the surface of the work. This idea is diametrically opposed to what I believe and do. I regularly use chisels with varying degrees of back bevel. While chopping a back bevel causes the chisel to go down into the wood straighter, when chopping with a single bevel chisel, the chisel wants to move away from the bevel. While parring, a back bevel raises the handle of the chisel allowing you to pare in the middle of large work without turning the chisel over, it gets the handle out of the way. This is more sensitive than turning the chisel over and riding the bevel. Riding the bevel raises the handle too high and you are unable to anchor the the work as well. A back bevel allows you to lower the handle while making a cut which turns the cut into a slicing cut which is more efficient.  When using edge tools it is much easier to slice the cutting edge thru the stuff than to just force the edge straight thru, it also give you more control of the cut. The trick to this is to anchor yourself to the work with the sides of you hand and your arms like a carver does. You must become the jig instead of the tool being the jig. It’s like holding a pencil and using your fingers to slide along an edge as marking gauge, or using your thumb as a stop for starting a saw cut.

A Slicing Cut

In some cases jigs are very helpful, but in some cases they are just a crutch that keeps you from developing skill. Watch this Mary May video and see how she is always anchored to the work, this is relevant to more than just carving, you can also see her rotate the chisels while making a cut, which makes it a slicing cut.

Posted in gateway skills, Wood Working | Tagged , , , , , | 3 Comments