Yay Tony! This is close to the process I used. Worked for me.
Thanks! Edley. On 25 Apr 2008 at 12:34, Tony Moss wrote: Date sent: Fri, 25 Apr 2008 12:34:40 +0100 From: Tony Moss <[EMAIL PROTECTED]> To: Sundial Mailing List <sundial@uni-koeln.de> Subject: Anodising aluminium > Hi all, > Following on from Chris' recommendations and for anyone new to the SML > here is a repeat of my instructions for simple home anodising of > aluminium. It really is a simple process which turns a dull and > lifeless metal into jewel-like material. Provided that good > ventilation and basic safety procedures are employed it is a very safe > procedure which produced hundreds of beautiful items made by students > over the years with no ill effects. > > Tony Moss > > ************************************** > > Anodising Aluminium in the Home Workshop > > 1. You will need a large acid-proof plastic container. Any > polyethylene bucket or tank will do into which your workpiece will fit > with a three inch gap all round. Alternatively I made purpose built > tanks out of marine plywood covered with a liquid-proof layer of > glass-fibre resin and surfacing tissue. After years of use these tanks > are still in good working order. > > Just one very large tank will serve but of course this will need a lot > of electrolyte. > > 2. Work outdoors or have good ventilation as the fine bubbles of gas > which rise to the surface produce an weak acidic mist which is barely > detectable - and then one day you discover you have lost your sense of > smell! N.B. It will return eventually but better not to risk it. > > 3. You can anodise with low voltage AC or DC but if you use AC the > `Cathode´ mentioned below MUST be of lead. > > 4 The cathode (negative connection) can be formed from a sheet of > aluminium bent to fit around the interior walls of your tank as a > loose `liner´. Leave a projection tab to bend over the edge of the > tank with a terminal to which the negative wire is connected if you > are using DC . If your power supply is AC then the cathode must be > sheet lead. > > 5. Part-fill the tank with electrolye made by adding one part of > concentrated sulphuric acid to nine parts of water. Wearing goggles > and rubber gloves pour the acid SLOWLY down the side of the tank into > the water. NOT the other way around. Pause if too much heat is > generated. > > 6. Experiment with a piece of aluminium plate about 3" square to get > the idea. Drill a hole in one corner and attach a pure aluminium wire > by clinching with pliers to ensure a sound contact. 1/16" aluminium > gas welding rods are perfect for this job. > > If contact with the wire is loose then the anodic film may form in the > joint and this will stop the process. Design items to allow > appropriate wire attachment - leave a cut-off tab or drill a hole in > the base into which a filed taper can be `wrung/seized´ tightly. > > Hollow items can be held on an expanding zig-zag made to spring open > into the inside. etc. etc. > > 7. Holding the object by the wire dip it into a strong solution of > caustic soda (Sodium Hydroxide (NaOH) for a few seconds until it > fizzes to remove natural oxides and grease. Rinse in clean water. Eye > and skin protection are vital here so goggles & rubber gloves are > recommended. > > 8. Suspend in the anodising tank supported from some kind of busbar. I > use a square brass bar over the tank drilled at intervals with screws > to clamp the wire into the holes and ensure a good contact. > > 9. Connect the positive lead of your power supply to the workpiece via > the busbar and the negative lead to the Cathode lining of the tank. > > 10. Set the voltage to about 16v and in a few minutes fine bubbles of > oxygen should rise from the workpiece. The oxygen produced by the > electrolysis of the water in the electrolyte combines with the > aluminium at the surface to produce crystal clear aluminium oxide > (grindstones are made from it!). > > The oxide is produced is microscopic `tubes´ rising from the surface > rather like a honeycomb. Electrical contact is maintained through the > tubes and new oxide continues to form at the base thickening the film. > > After about 20/30 minutes you can switch off the current, remove and > rinse in CLEAN water. The aluminium will have a whitish coating but DO > NOT TOUCH IT or you finger prints will be captured for ever! > > If the object is now immersed in a cool dye solution - there are > special dyes made for this but most household dyes work fairly well - > the dye molecules will fill the fine glassy tubes to colour the item. > Simply boiling in clean water for a few minutes will then cause the > outer ends of the tubes to swell and seal off leaving you with a > brightly coloured object which has a soft velvety feel and is > impervious to general wear and weather. > > To get metallic golds and bronzes you will have to enquire of > companies such as SANDOZ who may part with samples. They usually > supply in expensive 1kg tubs which contain enough for 1000 years of > home use. > > Voltage and Current > > Very small items such as rings and jewellery need a low voltage for a > long time whereas larger items need a higher voltage. > > I have a GIF of a voltage/current/time graph derived from experiment > which you can request when you get started but by setting 16 volts and > allowing the current to take care of itself will be a good beginning > from which to build up your own experience. > > Multi-colour anodising, photo-printing or writing on the anodic film > with felt tip pens etc. are all areasin which I achieved good results > and are there for you to experiment. > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > -- > No virus found in this incoming message. > Checked by AVG. > Version: 7.5.524 / Virus Database: 269.23.4/1395 - Release Date: > 4/24/2008 7:24 AM > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
