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Mixed Solid Media with Andy Ogilvie     Demo 2
Thu 20th June at MWCC Club Night 

 

 

 

SOLID MEDIA refers to different materials that can be worked.
These include :
 wood
 soft metal
 epoxy resin
 acrylic
 Perspex
 Corian
 Milliput epoxy putty
    etc

A piece of wood with just paint, pyrography or made out of 2 or more different types of wood doesn't strictly satisfy the criteria of
MIXED SOLID MEDIA, whereas, two or more combinations of the above examples does, whether used within the body of the piece, or as a decoration.
For example, Andy had used
 Perspex as a lid to his wooden kitchen Salt Pot to keep moisture out while able to see what was in that particular pot;
 turned Corian to enhance an opening;
 napkin rings decorated with Milliput;
 a Laburnum urn decorated with brass rivets.

(click for close up view)

(click for close up view)

In précis, Mixed Solid Media pieces can be :-
 ♦ COMBINATIONS of the above media or kits (egg timers, clocks, pens etc);
 ♦ DECORATIONS of solid media applied to a piece;
 ♦ INTEGRATED MATERIALS which form a blank for subsequent turning.

This demonstration will give more detail of how to achieve some of the above processes.
Andy warned that using open-grained wood had difficulty in maintaining a sharp edge between wood and putty/metal alloy once the piece had been sanded back to a smooth finish, because the slurry had a tendency to penetrate into the wood grain resulting in a cloudy grey effect near the joint between the media.
For his demonstration, he had chosen Boxwood.
Andy's basic message was, "Don't be put off with experimenting with these various materials just because they are unfamiliar. They are all manageable."
 

  Milliput Epoxy Putty
Milliput comes in 2-pack blocks of putty in black, yellow grey, silver grey, terracotta and superfine white, (the latter can be used for creating very fine details).  In preparation for applying his Milliput around the body of his box, Andy used a Parting Tool to create a recess about 3-4mm deep and about 5mm wide, although he deliberately countersunk the sides to be wider at the bottom of the recess in order to help secure the putty in position once cured. After cleaning the surfaces, he applied a coat of sanding sealer which would help keeping the wood clean with a simple wipe.

When new, the putty is malleable although it will be less so with age after opening.
   Top Tip   :  If putty has become stiff with age, try working each block separately while under the stream of warm air from a hairdryer but be aware that heating reduces the curing time and hence less time to manoeuvre into situ. Adding a little water can also soften the paste.

Having selected equal quantities of both parts, Andy mixed them well together before rolling out into a thin sausage and pressed into the recess while aiming to minimise gaps/holes. There was no need to skimp on the amount used because it cleans off easily and used for the next recess.  Andy often uses different width of recesses to create interest.

Depending upon temperature and age of putty, it would take about 2 - 3 hours for the Milliput to 'cook' and harden off enough before one could turn the piece with a gouge or sand back. Milliput can be readily shaped by gouge and particularly receptive to sanding.

Andy also described other effects that could be produced using different coloured putty like the black and white chequered feature shown below.


 

  Soft Metal
Andy had brought along some "Wood's Metal" bars of bismuth/lead/tin/cadmium alloy which have a surprising low melting temperature of 70ºC (not much hotter than solder) and would melt in a spoon with a hot air gun, particularly when the alloy bar is cut into tiny pieces.  He warned against using solder as it tended to be difficult to pour without solidifying before it filled up all the space and it doesn't polish up as well as the alloy.  Pewter is a suitable alternative but requires higher temperature to become molten.

As we are relying upon gravity to help us, trying to cast a metal ring around the side of the box is a difficult process. However, flat surfaces like a box lid are perfect.
So while the lid section of his box was still connected to its body on the lathe, he prepared as he had done for the putty by forming a countersunk recess into the end of the piece but then added a slight bevel to the edges of the recess; these bevels encourage the molten alloy to fall into the recess.
After cleaning the surfaces, he again treated with a coat of sanding sealer.

With the lid now set flat, the chips of alloy were placed in a spoon and heated with a hot air gun until molten about 45 seconds later when it was poured into the recess. Enough alloy was dropped in for the meniscus to just bulge above the prepared bevel. This was to allow for any dipping as the alloy cooled & solidified. Dependent upon the volume of alloy used, it should be ready to work within 10 to 30 minutes. The aim was to minimise wastage and to have very little to turn away with a gouge. Before any sanding, another coat of sanding sealer was applied and subsequent  abrasives were carefully used lightly with fine grits only & at a slow speed to avoid frictional heat re-melting the alloy.


 

  Integrated Resin
A quick Google search for "resin for beginners kit" will show there are many suppliers out there, which might seem daunting but can be rewarding with a little perseverance.  There are 3 types of resin; Epoxy, Polyester & Polyurethane but epoxy is best for gaining experience.  Many starting sets are for thin projects but woodturning projects tend to require several centimetres thickness, which you will need to consider before buying.
They all require mixing of the resin with a hardener. The deeper the cure mixture, the more that stirring and higher curing temperature can create bubbles which would detract from the finished article.  To overcome this problem, some suppliers sell specific epoxies & hardeners for different depths while some guide you to different ratios of resin to hardener. Others explain how to remove bubbles using heat guns or even toothpicks!  One method includes using pressure pots that will compress air bubbles to sizes so small that you will not be able to see them, in order to achieve a high quality clear casting at the cost of several hundreds of pounds Sterling!
Not surprisingly, the duration of the curing process is variable from maybe 10 - 24 hours so it is always best to leave the turning for at least a day.

"How to make a combination of wood and resin blank for turning" is best done by asking Google that very phrase and watching one of their helpful videos.
The basis is :
 Prepping the mould with the wood;
 Put in some means for the chuck jaws or screw chuck to grip;
 Tape the wood down so that it doesn't float away when the resin is poured in;
 Mix the resin and hardener;
 Stir in colour/sparkle as desired before pouring;
 and leave for at least 24 hours.

            (click for close up view)

Next day, you should have something like Andy's photo above; the Polyfilla tub acted as the mould and he has already used the lathe to create a new spigot for the base of the bowl whilst mounted in the jaws using the wooden spigot partially buried in the resin. Andy had found that warming up the hardener/catalyst seemed to help it mix with the resin more efficiently and he advocated leaving the mix still for 15 mins to give bubbles a chance to dissipate.  He had added a blue tint and some sparkles.

Much of the initial sanding of the resin piece was with a 50mm padded drill attachment but after fine abrasives and spray lacquer to finish, it looked like this ...

 (click for close up view)

The July 2024 Competition was set to turn any piece of combination, decorative or integrated styles that incorporates two or more Mixed Solid Media


A Cautionary Tale - Having seen some bamboo stalks encased in resin on You-Tube, Andy told of his attempt to incorporate this idea into one of his projects.  To the left, you can see the pot within which he had arranged a circle of bamboo to be set in some resin, somewhat mimicking an orange. After allowing to cure and fitted into a chuck, Andy experienced a catastrophic failure when upon starting the lathe, the resin failed to hold the whole piece together and the orange suddenly broke up into 'segments'.  You might spot in the photograph that some significantly large pieces detached themselves and indeed there is one piece still in the workshop somewhere he cannot find. The reason is uncertain but possibly a combination of excess moisture within the bamboo and the thinness of resin bridging the edge to the centre. As Andy is accustomed to do whenever he starts turning a new piece, particularly with an irregular shape on the lathe, he was wearing his face shield, which did exactly the job as its name implies.

(photos by Rick Patrick & Andy Ogilvie)
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