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Resin Stabilising Blanks 1: Introduction

Contents

  1. Introduction

  2. What is Resin Stabilising?

  3. Why Stabilise Wood?

  4. Suitable and Unsuitable Timbers

  5. Stabilising Resin

  6. Limitations

  7. What this is Not

  8. Equipment List

  9. The Stabilising Process

  10. Cost and Time

  11. Working with Stabilised Wood

  12. Links


NOTE: This and the other blogs in the series are work in progress. I will be adding to them as I get new materials and equipment to improve the range of topics covered.


The articles in this series are:

  1. Introduction (this article)

  2. Equipment and Materials

  3. The Stabilising Process

  4. Turning and Finishing Stabilised Timber (to follow)

  5. Adding Colour (to follow)


I hope to include a gallery section and project ideas in later blogs.


If you have any feedback, requests, comments or corrections, please let me know at robin.williams@tessellata.co.uk


There is some duplication in all the articles, particularly in the Introduction and the Links sections, and this is to make each article stand alone.

 

1. Introduction

Summary

This is the first in a series of blogs looking at Vacuum Resin Stabilising of wood blanks – from here on in I’ll just refer to ‘Stabilising’ to save time. This blog is an introduction looking at what stabilising is, what equipment and materials you need and a brief run-down of the process. Later articles will look at what you need and at these in more detail.


A range of Stabilised pen blanks
The photo shows a selection of stabilised pen blanks available from Tessellata.


Disclaimers

Where I have included costs, they are relevant at the time of publishing (April 2024) and are likely to change. The prices are provided for guidance only.


I mention TurnTex a lot in these articles as they are the suppliers of the resin and some of the main equipment required. I recommend the use of their products because I have found them to be the best I have tested. Tessellata Woodturning do not guarantee the resin or any other products in any way, other than those supplied by Tessellata. Details of the TurnTex Guarantee can be found on their web site. Tessellata is not associated in any way with TurnTex or their UK distributors.


See the Links section at the end of this article for links to both TurnTex and their distributors.


Measurements

Wherever possible, I have stuck to metric for the measurements and dimensions for consistency, so apologies for those still working in Imperial or other systems. There are plenty of conversion calculators online that will help in converting if required.

An important point that not all may be aware of is that US and imperial (UK) liquid measurements are not the same – for example, a US gallon is 3.79 litres whereas an imperial gallon is 4.54 litres – a sizeable difference.


Safety

Work safely to avoid accidents or injury.

  1. Always use the appropriate safety equipment. This includes goggles and a dust mask or ideally a full-face powered respirator. Wear nitrile gloves when handling resin.

  2. Containers under vacuum may fail, and when they do the results can be catastrophic. Never use damaged or worn-out parts. Inspect the pump, chamber, hoses and connectors before each use.

  3. Never leave the oven unattended and operate it in a well-ventilated area.

  4. Do not attempt to modify any of the equipment, particularly the chamber which must withstand high external pressures.

  5. Check your product manuals for any specific safety instructions and warnings.


2. What is Stabilising?

Some timbers, particularly those which are soft, porous, spalted or rotten can be stabilised by removing air from the pores with a vacuum pump, and then allowing the vacuum to draw a low viscosity resin into the timber as the pressure in the chamber is equalised. The timber is then placed in an oven at around 95°C (200°F) to cure the resin leaving a semi-hard plastic in the pores that strengthens the timber structure.

The resulting piece is heavier, harder and stronger than the original timber; the degree to which they are different depends on the timber, not only the species but even individual batches.


3. Why Stabilise?

For the most part, there is really no need to stabilise timber unless there is something wrong with it – i.e., it is too soft or rotten (but still structurally sound) to be able to turn.

There are a few reasons where stabilising could be used to treat the timber:

The Wood is Difficulty to Work

Wood that is too soft to work or is prone to tear-out or other structural issues can be strengthened with resin. Spalted timbers such as that shown below have been weakened by mould, and although the patterning looks attractive, the different bands of colour often have different densities and strengths; stabilising helps to even things out and hardens the worst effected parts.

However, stabilising is not a cure-all – it will not fix structurally unsound woods and will not make up for blunt or mishandled tools.


Spalted beech showing its unusual markings.
Spalted Beech - A wood that can be difficult to work may be improved with stabilising

To Improve the Strength of the Wood

The resin will improve the structural strength of the timber, making it more suitable for high stress uses where the finished piece will be roughly handled.

To Protect the Wood

The resin impregnated timber will withstand damp, rot, woodworm and insect attack significantly better than untreated wood, making the finished pieces more suitable for outside use. The stabilised timber will not be impervious to these things (except maybe woodworm), so some care is still needed, particularly keeping the surfaces clean and polished.

To Add Weight to the Wood

Heavier parts can feel more substantial, with pens having a reassuring weight when made with stabilised timber. As a very rough average, a standard pen blank (145mm x 19mm x19mm) is 10 to 20g heavier once stabilised – there is a wide range of variability based on timber type and even different batches of the same timber. The weight difference is noticeable when you pick up and compare the blanks.

To Colour the Wood

Dyes can be added to the resin to colour the timber, and unlike other colouring such as spirit stains and paints, the colour will permeate throughout the wood. Multiple colours can be added in stages to the blanks to create rainbow patterns in the timber. Doing this with spalted or burr timbers can lead to some interesting patterns where the dyes follow the uneven grain in the timber.

Using coloured resins will be covered in a later article.


4. Suitable and Unsuitable Timbers

What Makes a Good Stabilising Timber?

The best timbers to stabilise will ideally have at least one of the following features.

Porous – The resin needs somewhere to go! All timbers have pores in the sapwood, but these get compressed in some heartwoods so that in some cases the remaining airspace is minimal to non-existent.


A close-up of an Ash board
A close-up picture of some Ash, showing the porous grain structure.

Spalted –Spalting is caused by bacteria which leaves the structure of the timber lightweight and open, where the resin can easily penetrate deeply into the structure of the wood. Spalted timbers are also ideal for coloured resins – I will add an article later on using dyes with resin.

Burrs – Burrs are not always ideal for this as they can be quite densely packed, but if there is space for the resin to permeate the timber the resin will follow the burr and can show some interesting patterns.

Well-Figured – Timbers like birds-eye maple and pippy oak are another good option as again coloured resins will follow their own paths around the grain, often emphasising the figure.


Ideal Timbers

These timbers are porous and soft, so will easily accept the resin and will be strengthen by the process. Examples of these timbers are:

Elm – One of my favourite timbers but can be a little soft so ideal for this process.

American Mahogany, Sapele, Western Red Cedar – all these timbers are technically mahoganies, and all are suitable for stabilising.


Usable Timbers

These timbers can be stabilised, and in some cases, it is useful to do so - but in general the timber does not require stabilising. Examples are:

Oaks, particularly American Red or White Oak.

Zebrano – A porous timber, zebrano is also prone to tear-out. However, although stabilising can reduce the risk of tear-out, the resin will not fill some of the very large pores that can be found in the timber. These are best filled with black CA.

Black Walnut – Another good timber that can sometimes be light weight and soft so will benefit from the process.


Well, it will work…

… but why bother?

Many heavy hardwoods can be stabilised, and some (padauk comes to mind) are quite porous. But if the timber is in good condition, then you are not going to benefit much, if at all, from stabilising the wood. So given the expense, why bother? (Also, the padauk colour will leach into the resin leaving your whole batch a reddish orange).

Other timbers which fall into this group are many of the heavier exotic timbers such as Purpleheart and Bubinga, as well as some of the native fruitwoods such as Cherry and Pear.


Unsuitable Timbers

High density timbers such as African Blackwood and Lignum Vitae simply do not have the structure suitable for the resin to penetrate.

Oily timbers such as Goncalo Alves (Tigerwood) will repel the resin so these should also be avoided.


What Else can be Stabilised?

The TurnTex documentation lists the following materials as suitable for stabilising – I have not tried any of these yet, but they sound interesting – I will add a new article on the website when I get the chance to try them out.

  • Antler and Bone

  • Fabrics

  • Fibrous Organic Materials and Seed Pods

  • Porous stone


5. Stabilising Resin

The resin used for stabilising has two main properties:

  • It has a very low viscosity allowing it to penetrate deeply into the wood pores, and

  • It is heat cured, not chemically cured, so if stored correctly it will stay liquid for up to a year.

As far as I am aware, there is only one manufacturer of a suitable resin. This is known as Cactus Juice and is made by TurnTex, based in the US. The resin and some other TurnTex products are distributed in the UK by House of Resin – links to both of these companies are given at the end of this article and in the Links section of the web site.


Cactus Juice is available in 0.5 or 1 US Gallon containers (1.89 or 3.79 litres – for reference, an imperial gallon is 4.79 litres).

One other useful property of Cactus juice is that the equipment (that which comes into contact with resin, not the vacuum pump!) can be cleaned with nothing more than soapy water.


Activating the Resin

When you buy the stabilising resin, it comes with a small bottle of activator which needs to be added to the main resin to enable it to cure. This is not the same as the hardener that comes with epoxy resins as it does not start the curing process. As its name suggests it simply completes the chemical composition of the resin allowing it to cure when heated.

Do not activate the resin until it is needed; unactivated resin will last for three years while activated resin will only last one year.


6. Limitations

The Resin

The stabilising resin is not a filler, i.e., it will not fill gaps of more than about 0.5mm without forming bubbles. It is also not a glue – yes it will stick parts together, but that is not what it is designed for and any bond between parts should not be relied on.

Do not expect the stabilising resin to repair badly damaged wood, or wood with large gaps and holes; this is probably best left for use with epoxy resin if not for firewood.


Blank Size

There are three limiting factors for the size of blank that can be cured:

  1. I would not recommend trying to stabilise anything where the shortest distance from any side to the centre is more than 50 or 60mm. It may work, but it will need a very long time under vacuum.

  2. The chamber size will limit the length of any part. And remember that you need at least 100mm over the top of the blank and the vacuum inlet (50mm of resin over the blank and another 50mm of free air for the resin to foam up).

  3. Your oven size will limit how large your blanks can be. Toaster ovens have a chamber approximately 200 x 150mm, mini ovens will be larger, but still only around 300 x 200mm maximum. These sizes are ideal for pen blanks and small bowl blanks, but not for long spindles or larger bowl blanks.


Turning

The stabilising process is not a magic cure to fix all the faults in the timber or tools. Yes, it may reduce tear-out, but with blunt tools you may still have problems.


7. What this is Not

For those new to Resin Vacuum Stabilising, there are a few terms you may have heard about that are similar but are not the same.

Wood Hardeners

In the UK, many woodworkers, especially the DIYers, will be familiar with wood hardeners used to repair rotten window frames and the like. Although these seem to do a similar job, they are a localised treatment. They are not suitable for Vacuum stabilising as they will cure too fast. These treatments also contain anti-fungal ingredients which are toxic, so greater care is needed when applying them or when working with the hardened wood.

Epoxy Resins and Resin Casting

Epoxy resins are a two-part chemically curing resin used for decorative applications. The resin sets relatively quickly (even slow-cure resins tend to thicken within 30 minutes or so) and are too viscous to penetrate far into the timber. Epoxy resins are used in turning, but this is beyond the scope of this document.

Stabilised timbers can be used with epoxy resin.

Resin Degassing

This is the process where an uncured epoxy resin part is placed in a vacuum to remove as many air bubbles as possible. Again, this is not going to be covered here, only to say that you can use the equipment required for stabilising also for degassing, but not always the other way around (there will be notes on what to look for when buying equipment in the following article).


8. Equipment List

A later article will go into more detail on the equipment required, options available, and how to choose the main parts. It will also have a few recommendations for accessories that will help in the process.

PPE

This should go without saying, as PPE is always important when turning, but particularly so given the fine dust that is produced when turning stabilised wood. A good dust mask is a must, along with a full-face visor. Much more expensive, but worth the expense, is a full-face powered respirator.

Wear Nitrile gloves when handling resin-soaked parts or machinery.


Chamber

The first major component you will need is something to hold the resin and blanks that can hold a vacuum without any danger of failure. These range from what are really just metal saucepans with clear lids, to specialist chambers designed for stabilising.

I do recommend the latter, but these start at around £200 so are not a cheap option if you just want to get a taster.

Buying Tips:

  • If buying one of the steel ‘saucepan’ chambers from an online shopping site, make sure it has a tempered glass lid and not an acrylic one – and in my experience the acrylic lid WILL start to fail the first time you use it!

  • Do not get the largest chamber you can afford unless you really plan on stabilising large blanks – the smaller the chamber the less excess resin is required.


Pump

The second main component is a vacuum pump. All that is required is an oil-sealed single stage rotary vane vacuum pump – this may sound complicated but is one of the most basic types of vacuum pump. These are mostly used for refilling air conditioner and refrigeration systems.

Although nothing too fancy is required, make sure the pump can be left on for several days. Many of the pumps sold on the shopping sites have a duty cycle of only 30 minutes!

Buying Tips:

  • Make sure your pump has a continuous duty cycle. If it does not say this in the product listing, assume that it does not.

  • Make sure it is 240v and has a UK plug (assuming you are in the UK).


Gauge and Hoses


The lid of a TurnTex vacuum chamber
The lid of a TurnTex chamber showing gauge and connectors

The TurnTex chambers and the kits sold online should come with the required gauges and hoses, but if you are making up you own kit you will need:

  • An oil-filled vacuum gauge with suitable fittings for your lid.

  • A ¼” SAE T-Piece with suitable fittings for your lid.

  • A ¼” SAE tap with filtered input.

  • A quick release fitting to suit your hose and the T-Piece.

  • A non-collapsable hose with fittings for your pump at one end and a connector into the T-Piece at the other. This should be around 1.5m long.


Oven and Thermometer


A Toaster Oven with modified shelves and thermometer
The toaster oven I used when I started stabilising

Using your household oven is a bad idea – Although the chemicals used in the resin are non-toxic, they do smell when curing, and are not going to improve the taste of your food.

Make sure the plug has the correct fuse, and never leave the oven unattended while it is turned on.

What type of oven you buy depends a lot on how big and how many blanks you plan on working with at one time. My first oven shown here is a toaster oven bought online, but similar items are sold in homeware and electrical shops. These are cheap, but they are not ideal. There is no insulation in these ovens, so as much heat is lost from the sides and front as goes into the oven. This oven will cure 32 pen blanks or two 150mm x 50mm bowl blanks.

It is also worth spending a little on an oven thermometer, as the settings on the oven can be unreliable.


Moisture Meter

A moisture meter is useful to check the timber moisture content. Here cheap is fine – you are looking for a change in moisture levels rather than a super-accurate reading. Simply set your meter at its highest setting and take before and after readings. You will get more accurate readings by pushing the sensors in as far as possible, so don’t do this on an important area of the blank.

 

 9. The Stabilising Process

Below is a short run-down of the processes involved in stabilising wood. I will go into more detail in a later article.


Inspect the Equipment

Check all your kit is in good working order and that there is no damage to any of the components which must hold a vacuum.


Prepare the Blanks

Before stabilising, the blanks need to be cut to the size required – you want to waste as little resin as possible. It should also be sanded to remove loose fibres and then wiped clean to remove sawdust that would otherwise get into the resin.

It is very important that the blanks are as dry as possible, as any water will contaminate the resin and prevent it curing properly. TurnTex recommend you place it in an oven for 24 hours at 100°C – which seems excessive and costly but will provide the best results.

Alternative methods are to microwave the wood for five minutes at the lowest power setting and then rest them in a bag of desiccant repeat this process until no further change in weight is noted. I have tried this method, and it does work, but you do so at your own risk and never leave the microwave unattended.


Fill Chamber

Place the clean, dry blanks in the chamber and weigh them down to prevent them floating in the resin. The TurnTex chambers come with a plastic plate that grips to the side of the chamber, but alternatives are kitchen weights or weighted plates, as long as they do not move and keep all the blanks in place.

Next, fill the chamber with activated resin. The resin must completely cover the blanks, and there should be at least another 50mm of resin over the top of the blanks to allow the resin to penetrate the timber. You will also need at least another 50mm air space above the resin to the top of the chamber (or the vacuum input if your gauge is on the side of the chamber).


Apply Vacuum

Check the top of the chamber and the lid seal are clean and undamaged, then fit the lid.

Start the pump running and then slowly shut the tap on the lid. If your chamber is full then you will need to do this very carefully. As the pump starts to draw a vacuum, bubbles will form, and these will rapidly climb the chamber – you must avoid drawing any resin into the pump as this will most likely destroy the pump. If the bubbles start to rise too high, just ease off the tap until they start to subside and then continue.

Once the foam has settled down, leave the pump running until no further bubbles are seen. This can take several days, so you need to be patient. Keep monitoring the pump; it will get hot, but this should not be a problem. Regularly monitor the oil through the viewing window – if this becomes cloudy, or if you can no longer see the oil then you have a problem and will need to abandon the process.


Soak

Once no further bubbles are seen rising to the surface open the tap and then turn off the pump – it is important to do it in this order to avoid pump oil getting sucked back into the chamber.

Leave the blanks in the chamber to soak for at least twice as long as it took for the bubbles to stop.


Cure

Remove the blanks from the chamber, wipe off excess resin and place in a pre-heated oven at 90°C for about 2 hours. The actual time is roughly 45 minutes per 25mm thickness once the oven has returned to 90C, which can be 30 to 40 minutes with a small oven full of cold blanks. Higher temperatures will not harm the resin, but they can cause some resin to leak from the blanks.


Finish

Allow the blanks to cool in the oven and remove them when they are comfortable to handle. Excess resin can be removed with sandpaper.


10. Cost and Time

Equipment Cost

Setting up a stabilising system is not cheap. Yes, you can buy stabilising kits from the big online shopping companies, but these are often not suitable for resin stabilising, whatever they may say in the description. A good pump will cost the best part of £200 and even a small chamber can be the same. Once you add a mini oven, resin, pump oil and all the other odds and ends you are up to £600 plus before you start. You can cut some corners, and I will discuss some options in the following Equipment article, but it is still difficult to come in under £400.


Resin Use

The amount of resin needed is based on two things – the size of your chamber and the volume of the wood being stabilised. I found that when I filled my chamber with 32 blanks (enough to fill my oven) I needed four litres of resin. Once the process was complete, I put back around three litres, so one litre was either taken into the blanks or lost in the cleaning up process. The resin is not cheap, and this works out at around £28.00 of resin for each pass.


Time

My experience so far has been that one pass through the above process takes around eight days to complete. This is typically one day preparation, two days under vacuum, four days soaking and a final day curing and finishing the blanks.

Actual work time is of course much less. Most of the work is either end of the process – preparing the blanks and then curing and finishing, I would put it at around four hours actual work for a batch of pen blanks.

 

11. Working with Resin Stabilised Blanks

Stabilised blanks do not look greatly different to non-stabilised blanks – you may see some resin residue on the sides, but otherwise the wood does not look any different. What you will notice is the difference in weight – a stabilised pen blank can weigh 10 to 20g more than a non-stabilised blank.


A comparison of stabilised and unstabilised blanks
A stabilised (top) and unstabilised blank

The photo above shows a stabilised (top) and unstabilised zebrano blank. Both have been turned and finished the same way: sanded to 400-grit, sealed with sanding sealer, friction polish and then wax stick polish to finish. Although the stabilised blank looks a little lighter, I would put this down to variation in the timber, otherwise, you can see very little difference between the two.

The stabilised timber can be worked the same way as any other timber, except that it does not work so well with dyes, stains and other treatments meant to penetrate the timber – surface treatments work fine.

The most obvious thing you will notice when turning stabilised timber are the shavings – or lack of. However sharp your tools are, you will not get the wonderful streamer shavings you may expect, instead you get a fine dust, a mix of sawdust and resin dust. For this reason, a good dust mask is vital.

You do not need any special turning tools or equipment for stabilised blanks, nor is there any need to change your turning technique. Traditional tools and carbide cutters will both work the same way as they do with non-stabilised wood. It should go without saying that the tools still need to be sharp and in good condition.

 

12. Links

NOTE: These links will open in a new tab. The links go to external sites over which Tessellata has no control and are not associated in any way.


TurnTex

The main resin used for stabilising timber is Cactus Juice, manufactured by a US company called TurnTex:

If you have a Facebook account, I highly recommend joining the TurnTex LLC Facebook group – links can be found on the site above. The group is run by the owner of TurnTex, so the information found there is as reliable and up to date as possible.


House of Resin

The UK supplier of TurnTex products is the House of Resin:

 

 

The above article is Copyright 2024 Robin Williams, Tessellata Woodturning

 

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