TheAlchemist

Hi John, There is another way to approach the anti-corrosive propertiy, that is to use Micaceous Iron Oxide, MiO. This has the same platey form as found with leafing aluminium, but allows for a thicker dry film. (Better build). As we all know Iron oxide, red iron oxide, provides a degree of corrosion resistance, as attempted with all the red oxide wagons on all UK railways, this does not approach the reistance of either MiO or leafing aluminium, but is a cheaper alternative. At one time all the CEGB HV transmission towers were painted with a 3 coat system of MiO (different colour on each coat) to reveal misses, Holidays, by the operators. They ended up with a coat of grey. If you formulate with MiO and aluminium together you get both build and the plating effect, the Al acts as a white(!!) and adding black, carbon black, pigment then you can juggle the recipe to give a grey. The precise colour may be specified and then this becomes a formulating problem. In extremis some white pigment (titanium dioxide) can be added. Both the black and white have much greater hiding power than the MiO. Just a little from playing with these sort of things from 1961. One day I might retire. May I just add my appreciation of your work in this thread? Jerry

I just want to add some thoughts dredged from my days making aluminium paints. These are (were) made using so-called aluminium paste, that is aluminium flakes dispersed/milled into a solvent such as white spirit or xylene.By altering the chemistry of the paste either leafing or non-leafing types can be produced. Both process take a lot of experise to make consistently. (Beyond me) non-leafing types are used in the metallic finishes often used on motor cars in which you can easily see the individual flakes. Non-leafing aluminium yields the very bright silvery finish which you will often see on structural steel and ironwork and as a coating on bituminous felt roofing. The silvery effect seen on oil refineries and chemical plant is often due to this sort of coating rather than the often assumed stainless steel. This type is employed as the flakes literally act as leafs which plate to form a very effective light and moisture barrier. Hence their use on railway furniture as an aid to prevent corrosion of the underlying metalwork. Of course the binder which the paintmaker uses also has some bearing as it is that which provides adhesion, both to the substrate and also between the aluminium platelets, which can be less than optimal. Aluminium is a difficult substrate to get adhesion to. As the coating ages the aluminium is inevitably subject to attack and the initial brightness is seen to diminish. see this for some diagrams http://www.toyal-europe.com/fr/xlp-view.php, and http://www.silberline.com/BasicSection.aspx?id=342 This might be of interest when yo next try to estimate the time when the item was last painted! Jerry

After watching this thread for some time and admiring the handiworkf of others I know I need of some help. I have built several boxes based on the McKenzie & Holland type 3 drawing in the Signalling Study Group/OPC book of box designs but at present none have the outside steps. Why? i have no idea how to construct them to an approximation of scale. (P4) According to the Westinghouse drawing (plate 128) the stairs rose ~28' at about 45 degrees. Construction was all timber, treads 2'6"long x 7" x 1 3/4" with 8" rise between each of 13 treads. I have achieved a satisfactory CAD drawing to drive my laser cutter but how do I assemble everything to achieve a visually OK look, with each tread evenly spaced, horizontal side to side and not tilted.? As there are so many examples of realistic looking stairs bu contributors may I beg some advice? Jerry

The concept of mixing talc with your PVA has its origins in industrial practice. At one time various 'extenders' were used to 'knock the gloss off' paints and varnishes, with the use of barytes, calcium carbonate and/or silica being in common use for many years. The economics of manufacture and the ability to stir-in talc in the final colour matching phase to adjust the final gloss level became widely used. Fortunately talc does not contribute achange the paint or varnish colour beyond that which can be adjusted at this late stage The Alchemist.

I should have provided this link to the photos I meant. http://www.rmweb.co.uk/community/index.php?/topic/58228-the-stationmaster-looks-at-bourne-end-the-one-on-the-wycombe-branch/page__fromsearch__1 The Alchemist

I can't resist commenting on this site and the photographs around Bourne End. As a Maidonian I recall the big dip in the roadway of the level crossing in the late 50s-early 60s. Inspection of the 3rd picture from last will show what I mean, note the repairs. The dip had become a pothole at one time, I owned an MGA convertible, BMC B series engine, springs?, cross-ply tyres, original condition, no rust!, capable (just) of 100 down the hills into Marlow. Bourne End crossing was on the back route to Mhd, but not on the outward as the pothole was a deterrent after a few shattering journeys. Bucks CC came in for some commentary of an unfavourable kind, although with hindsight the roadway might have been the responsibility of BR. The crossing was often closed as we went to the pubs in Marlow and Cookham and the wait for the gates to open seemd to be an age, so we detaured around the local triangle rather than wait. Memories TheAlchemist