Mark Palma explores methods to deter bleed through
Adding colour or a decorative element to a turned object is a great way to it punch up. A finely defined band, colour or some other design element can really set a piece apart. However, if the design element is not well executed or the lines between it and surrounding areas are not well defined all that you tried to accomplish will be lost in the muddy barrier between the two areas. This boundary between either two design elements, or a design element and the surrounding wood, needs a way to achieve crisp definition. Let’s look at some methods to achieve your goal so that you can choose the one that is best for the situation you face.
Wood selection
After the complexity of your design, the choice of wood will probably have the largest impact of how much problem you will have with bleeding. Closed-grain woods (such as beech, birch, cherry and maple) generally control bleeding better because their texture and their cellular structure do not cause colourants, such as dyes, to flow within the structure of the wood itself.
Open-grain woods (ash and oak are common examples) are called ‘ring porous’ and allow not only sap but also dyes and colourants to flow through its cells. If you choose ring porous types of wood you will be creating a canvas that is difficult to control.
Adding a contrasting band
Many turners add a band of contrasting wood to their turning blanks in order to give colour and have a clean demarcation line. This is a great strategy if your design and blank permits such a plan. Segmenting turners have used this approach for years and achieved phenomenal results.
Grain direction
If you are adding designs, as opposed to a circular band, you can sometimes position the design element to so that the most complicated of the design will be with the grain and have less cross grain for bleed through. Of course, this does not work in every project, but it is something to consider whenever you can.
Turning in stages
This technique is very popular, however it does require you to plan ahead and dedicate a chuck to the project until you have completed all the steps. You need to think through the steps in advance as sometimes you have to cut your stages in a particular order. The overall concept is that you cut an element (or two) into a piece. Take the chuck off the lathe with the piece still attached and then do the colouring (and sometimes the finishing as well) on that element. Then, when you remount the piece you can cut right next to the coloured element(s) and get a very clean line between them and the adjacent wood.
There are difficulties in that any slip of the turning tool will ruin your coloured element. Sanding next to a completed element is a challenge. If you have open-grain woods you may need to put a finish on the colour before you return to the lathe, otherwise wood dust may become embedded in your colour and will be extremely difficult to completely remove (don’t ask me how I know). Even with a perfect cut, wood sometimes has a mind of its own and you may experience chip out or a sliver of wood ruining the crisp line you are trying to create. Despite the challenges, this is one of my favoured techniques. It has allowed me to create definition between round elements that would not have been within my ability with another technique. Another advantage of this method is that it allows airbrushing or spray painting an area and not worrying about overspray on to the remaining parts of the piece. I do mask my chucks before I ever finish with an attached chuck.
Colourant selection
The range of colouring methods available to us as woodturners is almost endless so I will only touch on a few. Hand-held colourants such as pencils, markers and inks allow someone with great hand control to achieve phenomenal definition between elements without using any other barriers or boundaries.
Very thin flowing liquids, such as inks and dyes, have a tendency to be difficult to keep within their intended areas. They like to flow right under masking tape, and even a deft hand with a fine brush will struggle with these products. You may find thicker colourants, such as acrylic paint, to be easier to control. For those of you who are skilled with an airbrush and stencils, you can add colour without overspray. The takeaway point is to not just grab whatever you have and expect it to work in any situation. If you want to use a particular colourant play to its strength, do not use it where it will fight you. To get a sense of what colourant will work best, take the time to do some testing on a scrap of similar species of wood. It is worth the time and may prevent you from ruining your work.
Use of design element
Consider the introduction of a bead, bevel, hard edge, or cove (or a combination thereof) when using colour. The size can be subtle, but the presence of some cut element can really help to keep a colour element from overflowing into a neighbouring area. If you look at many of the projects in this magazine from month to month, you will see a variation of this technique being used.
Temporary physical barriers
There are many products that can be used to mask off an area where you want to avoid colour or finish escaping from one area to another. In Issue 333 I wrote an extensive article on masking products so here I will not bore you with all the details. One key point is that high- quality masking tape seals off and creates a better barrier. Also, use a thin masking tape (I use automotive fine line tape) to follow curves and create the exact boundary between areas. Then mask off large areas beyond the fine line you are protecting with a second layer of wider tape. Sheet-type products allow for making stencils and protecting irregular areas. There are also liquid forms of masking products, although they may contaminate raw wood.
The real key to using temporary masking products is patience and meticulous technique. The line that will be revealed when you peel back the tape is only as crisp as your masking. So take your time, lift it up and reposition it as needed to achieve a smooth curve. Pull off the tape at a 45° angle and you want to remove it as soon as the colouring agent is dry enough that it will no longer flow. A pair of tweezers or a craft knife can be a great tool to grab the tape and keep your fingers from smearing the colour.
Burning and burnishing
There are many tools that allow you as a turner to burn or burnish wood to create a physical barrier between areas. Wire burning is an old and established technique. Using scraps of pressure-treated laminate (countertop) is another way to achieve the same result on a spinning lathe and allows expansion of the burned lines to rims and flat areas on turned work where a wire will not work. Pyrography tools take this to a limitless level and allow you to make designs off the lathe that cannot be created on spinning work. Whichever technique is right for your situation, this is a great way to contain colour elements.
It seems the act of burning or burnishing the wood seals off the end grain and better prevents dyes and inks escaping into areas you want to avoid colouring. In addition, as a side benefit the dark shadow line created may hide certain slips and sins when colouring, and allow touching up the edges with a fine-tipped marker – something I know from frequent personal experience.
Sealers
Often overlooked are the various sealers you can apply to your projects to protect certain areas chemically from colourants overflowing their intended section. Dewaxed shellac has been around for centuries and continues to be a great help. Shellac can be used over most colourants and many, but not all, can be used on top of shellac. This allows you to stop bleeding of colour from one area to another since the shellac has sealed the adjoining wood against accepting colour.
A formerly difficult problem has been solved by an epoxy sealer that is now available. This sealer can be mixed up to 50% with alcohol to create a clear barrier that can be applied to wood. I find that it is particularly helpful when pouring coloured acrylic elements in rims. The sealer can be painted with acrylic colours if you like. It really solves the problem of poured elements, although it can be used for whatever permanent chemical barrier you want to create.
Camouflage the barrier
Sometimes, despite all your precautions, you will have bleeding colours. At that stage there are a few things you can try to repair the situation or hide the problem. One option is to apply the lighter colour first, and then the darker colours will hide the overlap between the two colours. If that will not work, adding a contrasting outline of black with a pyrography tool or a fine marker (or paint pen) may be a viable solution.
Another approach is to either scrape or sand away the offending section with the point of a craft knife or a fine sanding stick. A lolly stick, some 220 grit abrasive and some adhesive will allow you to shape a sanding stick to any shape you need and sand into a tight area.
PHOTOGRAPHY BY MARK PALMA