M Wright

Hi, since last posting the laser has had the repaired power pack refitted, the spare one gave up quite quickly. I think this time it is not the board but a failed flyback transformer. I will another transformer and fit it sometime. I have started a new project with the cutter. I had a sudden desire to build a model of the first train that ran nearby on the Deeside Railway.(Scale O FS) The locomotive is still being drawn up so I can cut patterns for the engraving machine but the first coach has been realised. The coach was built by Joseph Wright in 1859 and is a 3 compartment saloon first. The material used is card, mount board for the floor and inner wall and three layers of 400 micron card for the panelled exterior. I cut the components and then shellaced them. Assembly was with shellac too and the model above has been coated lightly with car primer. I am quite pleased with the "sharpness" of the model. If you discount the cost of the laser this is a very cheap way to build stock. The surface to be painted looks good. It will be interesting comparing the card coach with etched coaches I have.

Hi, some progress has been made on Deeside. A coach to diagram 24 of the Deeside railway has been drawn up. It is described as a First Class coach, but is really a type of austere saloon. They were built by Joseph Wright in 1859. Partions were full height of pine boarding. Seating (still to made and fitted was buttoned black leather. The model has been enjoyable to make as its cost so far is minimal as long as the cost of the laser cutter is forgotten about. I have made it from mount board and 2 layers of 400 micron card. This was shellaced and assembled with shellac. The use of shellac and card is I hope in keeping with the spirit of the topic. The coach itself would be typical of the sort of thing rural railways would be looking to purchase at the end of the 19th century. Unlucky for the directors of the railway being planned at Castle Aching the gauge is O. The spray of car primer shows the crispness that the old fashioned shellaced card gives. I think I will produce an etch to get me the parts for the underframe. In O scale I believe the correct buffers, springs and lamp tops are made by SER kits.

Hi, thank you so much for your opinion. I had a look at the DJH Ivatt 2-6-0 but I did not think it quite caught the loco. The made up models on the ACME site did seem closer to how I remember them. I will find your account of the Ivatt tank build, for I am sure there will be bits that are quite similar between the locos. The ROD will have to wait until I have time to make a copy of that nice bending plate that Metalsmith used to produce. I think that is what I need to make bending the tender flares simpler. Thanks again for the info.

Hi, I was wondering have you built any kits made by Acme? Were they a challenge or not? Have you ever built a Gladator kit for a GWR 30xx ROD? I know this kit should not be a challenge but I was wondering if you had ever posted about building one. I always enjoy your building tips, sharing your experiences must save many of us from time wasting errors. Thanks.

Hi, thank you Nick for that useful information. I have started to draw up a front view. It does'nt look bad with a 7 foot 6 inch beam and buffers at 5 foot 10 inch centres. The boiler has to be about 3 feet 9 inches over the claddding and that makes the smokebox between 4 feet and 4 feet 3 in diameter. Once I have decided on the the distance beween the frames, and the width over the wheel faces I can see how much clearance is left for the crosshead and then of course see if in the over piston faces can be contained within the 7 ' 6" of the buffer beam. From the only piece of information available - the picture on the cover of Parr's The Royal Deeside Line and photos I think they might have extended outside this. Consequently I would then have to narrow the loco from 7' 6" to 7'. In the end if there are inadequate drawing one just has to guess.

Sorry the photo got lost from the post. A photo showing the loco. This was before the GNOS was linked to the Deeside railway. Its only connection was to the Scottish Central in Aberdeen. I expect she and her sisters arrived by sea rather that pay for passage over the SC and the fearful prices of the NB. Scot's Blue it is a traditional colour used in interiors (those few that could afford to tint or colour wash their walls which of couse would need the indulgence of plaster) The colour is variable, I believe it is a cheap iron based pigment. The lightest I have seen was Hairbell Blue (very light) the typical tint is under the modern decoration in one room of our old house. The walls were painted blue in a shade used on the Saltire. This itself seems to have today two shades one a dark, almost navy blue (probably from woad or indigo) the other almost sky blue. I think Deeside Railway blue was the darker blue.(iron pigment) Thank heavens I am not modelling one of the early tank locos. One of these was painted in Royal Stuart tartan. No doubt to please Queen Victoria who used the restricted tartan palette exclusively for the decoration of her newly re-modelled Balmoral.

Hi,when I said the loco I was building was long boilered I was using the term in the technical sense. It was the loco's appearance - long and low. I think Deeside No 4 was also " strong and stable" when you consider the 2 mile ascent westbound from Banchory at 1 : 60. That is the railway that was and is a cycle path near our house. I still need suggestions as to width. It is being built in O gauge. I do have one drawing of the time, a Sharp Stewart 2-4-0 and tender. That loco is 7 feet 6 inches wide with buffer centres at 5 feet 10 inches. If I cannot have some widths suggested O gauge will be very appropriate since it will have to be built in the German style as a flat. Edwardians very helpful photo is certainly a close cousin and tells me a lot about the front end. Thank you so much for posting it. Northroader, thank you too. Similar dimentions to the Sharpie. I will leave the tank locos to another time, one of them by repute was in Royal Stuart tartan to appeal to the Queen. Who was as we all know so fond of the tartan colour for interior decoration.The late Hugh Gordon was a friend of my wife's family (he gave me the side view drawing of No 4 long ago.) A photo showing the loco. This was before the GNOS was linked to the Deeside railway. Its only connection was to the Scottish Central in Aberdeen. I expect she and her sisters arrived by sea rather that pay for passage over the SC and the fearful prices of the NB. Her livery was Scot's Blue lined with black. That must have been a bonnie sight on a dreich Deeside day.

Hi, this is a bit of a cheat but I have tried the rest on the "Scratchbuilding topic" I am now going to try the best. I hav'nt contributed to this topic before but it is the only topic that I have read from start to finish. There is so much information to be had here and the banter is of Footlights Review quality. Enough flattery, here is a copy of what I posted- "Hi, I have got the urge to build a model of a locomotive that ran close to our house in the 1860s.This is a loco built by Hawthorn and is a long boilered 0-4-2. There is a good drawing of the locomotive that was produced by the late Hugh Gordon however it like many drawings does not have a front view. So my first question to you all is given that the coaching stock of the railway was 8 feet wide, how wide do you think a locomotive of this type and date was? I have one works drawing from a decade later - a Sharp Stewart 2-4-0 built for the Furness Railway in the late 1860s. The distance between its buffer centres is 5 feet 10 inches and its buffer beam is 7 feet 6 inches wide. The width over the footplates is 7 feet 3 inches. The locomotive I am going to build though has outside cylinders, does anybody know the width of the early Beattie LSWR locos since they are of a similar type and build date? "

I had hoped some reader would have this sort after information. How wide were locomotives in the Victorian era? Looking on the web and flipping through the standard texts (Ahrons) whilst length and height are usually reported, width rarely is. Is that because most early drawings and prints for public consumption were side views? 3/4 views only seem to have become popular as the 19th century got into its final decades. I surmise it was only with the faster photographic emulsions that lineside photography slowly took over from formal side on presentation. Was it also that this was a period of cultural change. The static posed loco was losing interest as the working study of power and movement interested the viewer? However this does not help me. I still would welcome views on width, also when did buffer height and spacing start to settle into a standard? Replies please. Thanks in anticipation.

Hi, I have got the urge to build a model of a locomotive that ran close to our house in the 1860s.This is a loco built by Hawthorn and is a long boilered 0-4-2. There is a good drawing of the locomotive that was produced by the late Hugh Gordon however it like many drawings does not have a front view. So my first question to you all is given that the coaching stock of the railway was 8 feet wide, how wide do you think a locomotive of this type and date was? I have one works drawing from a decade later - a Sharp Stewart 2-4-0 built for the Furness Railway in the late 1860s. The distance between its buffer centres is 5 feet 10 inches and its buffer beam is 7 feet 6 inches wide. The width over the footplates is 7 feet 3 inches. The locomotive I am going to build though has outside cylinders, does anybody know the width of the early Beattie LSWR locos since they are of a similar type and build date?

Hi, great to see you back building a very nice looking CR loco. I do not know if it is of help but if you follow this link http://www.stationroadsteam.co.uk/stock%20pages/3052/index.htm you should find a few photos of your chosen loco built in 5 inch gauge by someone who knew what they were doing and I suspect had access to research materials not available on the web. Probably the St Rollox works photos in the Hunterian Library in Glasgow.

Hi, well since last writing I have had a replacement power supplly fail suddenly but gently. Since no fuses went I think it needs a new fly back transformer so I will try to fix it soon. In the mean time I have been very busy building steam engines but did find a couple of hours to re-fit the original home repaired power supply. Crossing fingers I turned on the power and it worked. So that is a learning curve knocked on the head until it fails again. Not having much time to play I decided I would try and make a gift for a pal. I wondered if I could make him some O scalish bracken. His railway has started to grow scenery and I thought some ferns and bracken would be an interesting addition. I decided to cut the shapes from 110g paper that was green in colour. I would then, using gel super glue, attach the bracken to a thin copper wire. Spray it with car paint to give it some strength and then twist and form the stems to shape. The photos show how I got on. To start with the parts are very fine. The whole cut out is 3 foot high in scale so much of the detail is sub-millimeter. To draw it up for cutting I cheated. I slapped a frond down on the A3 scanner. Converted the scan to a B and W image. Then used the trace tool and simplify path tool to get a reasonable outline trace. The final stage was to go over the image editing it without losing too much character (I hope!). The first attempt at a cut was OK ish. Alas many of the tiny details were vapourised no matter what power and speed combitations were tried. I then had a lucky break I was watching a You tube video on CNC plasma cutting steel by an artisan. To minimise fumes in his workshop he covered the steel with 1 cm of water. His technique worked and had other advantages too. I wondered if I could try laser cutting wet paper. Answer- a total YES. NO charring. NO vapourisation of tiny details and the paper held enough strength to be picked off the steel cutting bed I made (I use small magnets to hold card/paper flat) leaving the tiny parts behind. Cutting speed is increased and so is the power possible to use. So cutting these large files takes 50s dry paper/ 18s wet. I think this might be a valuable technique for making such small parts commercially.

Hi, I thought this might interest you. It is a project one of the guys who helped me fix my power supply is crowd sourcing. I am sure he would be interested in your project to fit a better processor to your machine. https://www.kickstarter.com/projects/2118335444/gerbil-the-open-upgrade-for-your-k40-laser?ref=creator_nav. Regards, Malcolm Wright (workwright)

Hi, you seem to be having fun with your upcycling project. One little set of tools I purchased for a totally diiferent job has proved a couple of times the cats wiskers when dealing with Chinese metal case and fixture design. It is made by their ex friends across the Sea of Japan. It is a minature ratchet drive and assorted bits + Hex and torx. It is made By Makita and is of very high quality. It is amazing with the little ratchet wrench in your fist what you can get into and undo . http://www.powertoolworld.co.uk/makita-p-79158-39-pcs-screwdriver-set#gref (cheapest I could find, no endorsment of poduct or supplier intended) The other essential on the 50w machine is my mountain bikers headlamp. Hands free and lots of light where you want it. The mounting of the electronic components in my machine is really c..p. Just put a self taspper through the case, woops, missed the wire, I think I will have another go. Never mind the razor sharp screw ends hiding under one of the beams that makes cleaning up cutting a rather bloody task. It will be interesting to hear how you fair with better quality components. Make sure all the components are earth bonded. Earthing seems little understood by their designers Regards, Workwright.

Hi, I would dust off your Taylor H. Why they were used and still are by a few is in helping to make masters for lost wax casting. The advatage over CNC (cheap) is that the machine is very ridgid and very accurate when set up. For O gauge a common ratio of pattern to part would be 4 : 1 ie any error is 4X smaller. To some extent the rididity of the machine and certainly the ease of use increases as the ratio becomes larger. Anyway back to what this topic is about. Does the emblaser have air assist on the laser head? Does it have any form of air extraction from the workspace? Is there a focus lens in the laser head? Regards.

Nice to see an engraving machine being used. Most of the great model makers of the last 50 years used a Taylor Hobson or Alexander engraving machine. They used to be very sort after. I paid over £1000 for mine 30 years ago, now with cheap CNC millers available you see them on e-bay for a couple of hundered pounds. The best cutters to use on them in my opinion are not the classic D bit type but solid carbide cutters. They last for ages and they will work dry on steel with the machine running at 15,000 rpm. I use old bits of Formica to make the cutting patterns. I wonder if I can laser cut this....... must find out.

Hi Simond et al, I post on most forums as "workwright". Your upgrade sounds very interesting, if you have time you should post it as well on the 40W and 50W chinese laser sites. At the moment all is quiet with the laser I am busy trying to finish a batch of steam engines so feel guilty if I take time off to do my own stuff. The only laser related task in the workshop is the repair of my broken power pack. With the help of a most helpful and generous(with his time)guy in the US I think I have finally found the broken component on the power supply board. Just waiting on the new diodes to effect the repair. Please take care when working on your CO2 laser. Remember even the small laser power supplies have very high voltages in them, more than enough to kill many times over. So remember when working on the circuit boards power supply capacitors take at least an hour to discharge. I always carefully check them with a HV insulated probe wired to a GOOD EARTH before going anywhere near. It does seem a real advantage of these blue laser light cutters they are not so dangerous it terms of voltages.

Hi SImond, No marble and tiles have the same problem as glass. Both these materials absorb CO2 laser light. The best absorber of common materials is clear acrylic (perspex) That is why it is engraved and cut so much. To the CO2 laser beam it is like black is to us so absrbs the energy of the beam readily. It take time to grasp that different frequencies of light have such different properties The work table of your laser is probably made of Aluminium. It is highly reflective to this type of laser as is copper and molydenium ( these materials are often used to make the mirrors of the laser. You are protected by the acrylic window in you laser lid. ie any scattered laser light by the Alumiium table for example, is absorbed by the perspex lid, therefore is kept safe inside the box. It is also why any pair of plastic lens safety specs are a good defence from the CO2 laser beam) Steel is a poor reflector and a reasonable absorber of your laser's light so makes a good base to work on. The cheap neodinium magnets off e-bay (1mm thick 6mm dia) make excellent holding devices on the steel but remember you have to slide them off not pull. TO get the best from your machine please watch some of these videos, they have saved me much heart ache and wasted materials. I have put a link here https://www.youtube.com/watch?v=YvrMeUUzaBo. I am sure you will enjoy them. Have you looked at my post on this page of the forum. It has got some info in it. I have tried to keep to a minimum the "hey there, see what I can do" but I hope I have conveyed my enthusiasm for what these machines with a bit of effort can do. I have found Giles Favell's posts on the emblaser thread insirational. I just cannot see how such stunning results can come from 3 or 4Watts of laser power.

Hi, I was reading these interesting posts when I read Simond's problem with his cutter base becoming contaminated with cutting grime. I realise that his laser is a CO2 one and have to caution him not to use glass as a cutting base. You can engrave glass with aCO2 laser therefore it absorbs the 10.6 nm wavelength laser beam and converts it to heat. The glass might (will) break. The best solution is to use a pin table. Use the laser to mark out holes on a grid in some 4-6mm acrylic. Drill holes a push fit for some 1" panel pins and rest the job on top. (I di not know your laser power but a 40W should be able to drill the holes too with a bit of luck. Another useful table is a bit of steel plate. Gunge comes off with a spray of WD40 and a wipe. If cutting card/paper/tissue it can be help to the plate using cheap small neodynium magnets. Look at Russ Sadler's (Sabar) You tube videos for real solid information and loads of ideas for getting the best out of Chinese Laser machines. All the best, regards.

Hi Jon, I have tried to get in touch with Surrey and Hants makerspace through Slack. I have to admit, so far, I am too stupid to work out how to do it. Is there a simple way I can e-mail them. Regards.

Hi, Nick and Jon. First the machine I purchased was from e-bay I will not name the e-bay seller until my dispute with them via Pay-pal is resolved. I think I am on the verge of anger with pay-pal since they said they would arbitrate and give me their decision on June 7th and they have now put this back to July2nd!. My issue was the failed power pack. The seller stated the machine had a three year warranty, but it was meaningless, the postage they wanted for the replacement power pack (£70) was £5 less than what they were sellinga new power pack for! I purchased another from a UK seller. A 40w supply and so far it is working OK. The machine was good value however. It was correctly set up and had an electric lift table. It cost £1060 inc p and p. So far I am happy with it but when the power supply goes it is a big bang and my heart certainly missed a beat! THe machineis accurate and the RD works software that comes with it is good. It imports Adobe illustrator files with no scaling problems, I regard it as well up to the job of driving the machine. Further the RD works software can work in terms of cutting with both vector and bitmap information simultaneously, integrating the information into a cutting/engraving plan. I would only consider purchase though after taking time to watch some/most of the You tube videos on the Chinese 50W laser cutter made by Russ Sadler. There is also a very helpful support group for the machine to be found at RDworks lab .com forum.(you join by invitation) The site has available an English (not Chinglish) version of the RD works manual on the forum. Jon thank you so much for that piece of information. I am starting to contact them. I have had help from some guys in the US and Holland with the power pack. They had a list of parts most likely to break. So beside replacing the fuse I have just replaced the rectifier chip that had also blown but alas it all went bang again when the repaired unit was plugged in. At the moment I hav'nt got the time to replace the fuse, test the rectiier, and replace them before finding what else has blown. Even with buying the parts from China the cost soon mounts up. It would be great to get a settlement from pay-pal then at least I could buy another power supply and keep it as a spare.Regards

Hi, well since last writing I have had a disaster with the laser cutter. BANG was the start. A very loud bang which turned out to be the main fuse and the power supply fuse going. Right in the middle of cutting for no reason at all. The ebay suppliers warranty proved useless and I am now seeking some redress through Pay-pal which again is grinding on very slowly. I did solve my problem though. I purchased a new power supply and fitted it. SO far it is still working but I did have to re-find all the best powers and feed rates for cutting. What I have done with the machine is illustrated below. Project (1) was to make a reasonable attempt at building a model of Arica Station in Chile. There are only 3 or 4 photos of the building. Using the children to get a scale I came up with a main building 44 feet long, 16 feet wide and 14 foot high. The tower top being about 36 feet above ground level. Below is a picture of the model I made. The windows are different - a pal had purchased some Grandt line windows in the US for me. It seems to have got the look I think and the extraordinary canopy supports seem about right. Anyway I do not think anybody will come up to me with the architects drawing in the near future. The original was destroyed in a tidal wave sometime in the 1900s I believe. The next project (2) was to make a few hundered channel tiles (Roman Tiles) I had cut a paper pattern from a tile in France. I drew the tile up from this and came up with an A4 sheet that gave we 300 or so in 6 minutes of laser cutting. First I had painted the card both sides with emulsion paint. When dry I left it for few days with a weight on top to get it flat. It was then laser cut. The tiles were very effectively weathered by the smoke in the laser. Before use each tile was curved round a needle file handle. The wall itself was thick hard foam embossed with large blocks to represent Adobe. The wall was then tapered at the top and covered with Gyproc filler. It dried to look like the desired lime render and in a few places this was abraded to reveal the underlying blocks. The next photo shows the wall end and the baggage/ goods enclosure together with the endview of the station building (compare to the prototype above) The baggage enclosure again was a couple of minutes cutting on the laser. The last holiday project (3) was to build 3 Palm trees that the station area required. Drawing the archetype palm frond did take a long time (about 2 1/2 hours) but once done simple manipulation in the drawing program allowed a lot of derivitives to be created. The fronds were cut 12 at a time on an A4 sheet of thin card (cutting time was 15 minutes) The card was then sprayed with car primer and a dark green car paint. The frond was then stuck along its stem onto florist's wire using gel super glue. The frond could then be bent and the card folded etc to give a pleasing form. The trunk was thick electrical cable wrapped in sisal string, raffia, and coated with plaster. The base and top were built up in wood filler from photos to get the right shapes. The fronds were inserted into pre-drilled holes and retained with super glue. The results are quite lifelike I think. The fact that each frond has up to 100+ leaflets helps. The palm behind the station is about a foot tall and has about 40 fronds,the nearer about 30 fronds only possible because the laser does'nt get bored cutting them out. The resulting complexity of the model does a good job to con the eye and brain I think. So in spite of the bang I am getting to like my chinese laser. It certainly lets you make things that go together, Make things that would be difficult to cut out with scissors or a knife and engrave (station name plates) It is a precise machine and seems to hold its precision over the whole 500 x 300mm cutting area.

Hi, Giles I have been a very keen follower of your modelling. A superb redition of a Garratt in Roy Links mag, the paint finish you achieved really set the model apart. You are partly to blame for my 50W purchase. I have very little time for my own modelling being in retirement my comercial model making has priority. When I first read your posts you also seem a guy with a great deal going on in their life so I was very interested when you make the transition from static grass to laser. The blue light Emblaser seems to achieve a great deal with so few Watts. The software is more substantial I think than the RDworks. My choice of laser type was guided by a pal who is employed making models and mounts for one of the great museums in the UK. His workshop has a nice 40W Epilog machine. A CO2 laser but in a different league to the glass tube in the Chinese machine in terms of duty cycle and lifetime. However they do share speed of cut. I do not feel quite so guilty standing 10 minutes by the machine while it cuts out 400 O scale Spanish tile blanks as I would standing for 20 minutes. You seem to be developing a tremendous skill in making brickwork. The nearest I come to file size so far are A4 sheets of palm fronds. I need 2 tall Chilean Oil Palms for the station area of my South American railway I build in my holidays. I will post some more bits and bobs I have been cutting for myself. When I think I am on top of the machine I will try to make some 16mm stock kits. Some Gwalior Light Railway coaches will be the first project. Thanks for the comment, regards.

Hi, I purchased this 50W Chinese laser in March via e-bay. I paid using Pay-pal which provides some hope of recovering your money if you need to. The 100Kg machine arrived in a van, driven by a girl who had been sent out without handling equipment. So the first problem was to get it out of the van. Who said 10 1/4" gauge track would be a useless investment? If it had not been for my length of prefabricated track that cutter would still be in the van. Down the ramp and on the ground and 56 coach screws later the 65Kg uncased machine was on a trolley ready to be taken to the laser room. The room was an emptied bedroom of a child long since departed the nest. Before plugging it in a couple of weeks were spent making a bench by a window for fume extraction and sourcing a water tank. If anyone wants to follow my example make sure you view some of the 100+ You tube videos made by Russ This will open your eyes to the plus and minus of these machines and most importantly get you started safely. The main problem with these machines is that they are potentially overdriven. ie more power is supplied to the laser than it can use so this rapidly causes the tube to degrade. You must not use the software power settings as any guide to how much power is going through the tube. It is essential to fit a milliammeter in the RETURN (Cathode) of the laser tube. There are several You Tube videos on how to this SAFELY. The maximum safe current in the return for a longlife in this wattage of tube is 16mA. This shows the Maplin enclosure with the mA meter, and coolant water temperature probe ( both£3 off e-bay) The water tank contains a cheap aquarium heater for winter use and to avoid termal shock to the laser tube. It is best to keep the coolant between 15C and 25C. Again if the temperature of the coolant goes much above 30C the tube loses power and can suffer permanent damage. The software that comes with the machine is called RDworks. Many users find it a bit wanting but I have not. It is limited as a drawing tool but is essential for processing the drawing to drive the laser. It allows different coloured lines on your drawing to either be cut or engraved. It allows bit maps and vectors to be combined in composing one cutting tool. Hidden from view is has some neat tricks. It allows the machine to optimise the cutting path for speed. It allows you to cut on the line or inside or outside it. The Kerf of the cutter is about 0.15mm-0.2mm.(the focussed laser beam is 0.1mm) SO it is possible to make parts that fit correctly. So what will it do? It will cut paper, mount card,plywood up to 6mm, MDF up to 6-8mm, acrylic (pespex) up to 6mm, These are single pass cuts at speed of 100-30mm/s for paper and cards, MDF 35-5mm/s depending on thickness and about the same for perspex. The original drawing is done in Freehand and old program like Illustrator. The files are drawn as hairline, exported as AI files into RD works where they can be further worked on eg they can be selected, re-scaled, coloured for different cutting protocols. In short it all worked. My first project, cut in 2mm, 3mm and 5mm perspex was to make a kit for a quarry slab truck in 16mm scale. The laser cut parts were assembled with Plastic Weld, The wheels are Binnie on shortened axles and the details- coupling hooks Binnie, nut and bolt castings-Cambrian. Time to cut the parts 2 minutes. Now that is much quicker and cheaper than any other way to make a quantity of wagons. The only kit part that needed a jig and a bit of thought was the through wagon draw bar. The cost of the perspex per wagon is about £1.

Hi, I have had problems with the white crud. My prepartion of cleaning is the same as yours essentiallly.First aabrasive cleaning with tooth brush and cream cleaner. Then I use a powerful ultrasonic cleaner filled with dishwasher powder dissolved in hot water. After cleaning and drying the white powder develops at the joint edges where solder paint was used. It is I think zinc chloride,either from the solder paint flux itself or the corrosion of the joint due to the residual flux. I tried neutralising the flux not with caustic soda but with a solution of washing soda. This was not a permanent solution. The best results were got by toothbrushing the model with about 20% hydrochloric acid before ultrasonic cleaning. All the residue vanished never to reappear. This was the system I used for a time. Another advantage was the metal, acic cleaned, took the Birchwood Casey blackening solution more evenly and faster. When I have blackened brass or NS I use after washing and drying Electrofix. My bottle of Electrofix was an orange liquid obtained from Carr about 30 years ago. If is now colourles but seems to act as a micro coating to the finished blackened metal. I think it also stops any further reaction. In the end I gave up solder paint and the RSU. I got too worried by the fumes. I now use solder creams, These have no corrosive flux ,just rosin, and if you buy 500g pots(they keep for ever in the fridge) It is easy to fill a syringe with a spatula. Fitted with a canula needle they make large or tiny soldering jobs a dream with the RSU. The other advantage is no white crud. The flux rosin just flakes off when cold. The solder creams were invented for screen printing the contact pads in printed circuit work so they are very fine solders usually tin/silver alloys that flow well. (The only downside is cost - typically a 20 g syringe pre-filled cost £20 but a 500g pot costs between £60 -£90 depending on the silver content and the complexity of the chemistry) I build commercially in large scale (16mm) A 20g syringe is enough for 5 locos, using the cream for assembly, detailing and fixing large detail overlays like frame sides, so you would probably find the 20g syringe more than adequate. Being a good Scot I thought in the long run I would save money with my bulk puchase!