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Post by 92220 on Jun 7, 2020 10:20:30 GMT
Hi Roger.
In simple terms, all paints are made by adding powdered pigment to a varnish carrier. The pigment powder gets thoroughly mixed in and micronised during manufacture, but after being tinned, it can stand for a long time before being used. How many times have we bought a tin of paint to paint something in the house and then put the lid back on and stuck it away in a cupboard because only a few brushfulls have been used. 3 years later we get the tin out again, and because the tin is, for all practical purposes, still full, the paint is still liquid and able to be used. When you take the lid off the first thing you notice is that the paint doesn't look anything like the colour it should. In fact it will look like a murky tin of varnish. The pigment, over the time it has been stored, will have settled towards the bottom of the tin. It may well not have packed down hard, but the concentration of pigments will be far greater towards the bottom of the tin, than it is at the top. In fact after about 12 months storage, the pigment concentration at the top of the tin will be around 25% to 50% of what it is when it comes off the production line. Leave it for 3 years and the pigment concentration will be near 0% at the top of the tin. As far as making Black paint goes, it's no different to making Vermilion paint, basically. It is a coloured powder mixed into a clear varnish, along with other chemicals. When I was making paint, I bought 50Kg bags of carbon black pigment, mixed it into the resin, added driers and solvents to thin the mixture, added surfactants to help the resins adhere to the pigment, and in turn adhere to to painted surface. The whole mix was them passed through the bead mill 2 or 3 times, until the pigment size was sub micron. All paints will settle out over time so you are quite right, to make your tin holder and mixer, for the painting. Anyone who doesn't mix thoroughly will NOT get the ultimate finish.
Others might disagree with me but I do have over 30 years actually making paints from basic raw materials, and sorting out model engineers and modellers painting problems. Keep up the good work and keep posting. You are approaching the painting in exactly the right way!!
Bob.
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Post by 92220 on Jun 7, 2020 9:41:33 GMT
Hi Roger.
What Chris suggests is the best way to go. Don't varnish over the whole surface, just lip the vanish over the transfers and JUST ENOUGH over the edge of the transfer to seal the edges, but not enough to be obvious. The reason for varnishing transfers is that the adhesive is a very mild one that dampness in the air can cause loss of adhesion. Also, as Dave (kipford) says, applying transfers to gloss (or just off gloss) is best. Trying to apply them to a matt finish will cause problems due to the microscopic 'dustyness' of the matt surface. The transfer adhesive isn't strong enough to hold the transfers down effectively on the matt finish. The way all paints are made matt is that micronised talc is mixed into the gloss paint, and when it is painted out and dried, the microscopic crystals (between 5 and 0.5 micron) project from the surface of the gloss paint, and reflect light in all directions, so the eye sees it as a matt finish. These crystals break up very easily and become dust on the surface, spoiling the adhesion of the transfers.
Bob.
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Post by 92220 on Jun 7, 2020 9:29:22 GMT
Hi Roger. When the mixer is in the tin and it is held in the jig you printed, just gently bring down the drill quill, while revolving, to just rub on the bottom for a few seconds. The mixer will get close enough into the corner to drag out the pigment. Unless the paint has been standing for 2 or 3 years, the pigment won't have gone so hard that a few seconds won't get it loosened. If it is old paint, either break it loose with a screwdriver, as you suggested, or just run the mixer scraping the bottom for around half a minute, at around 1000 rpm. Once loosened, raise the mixing speed to the highest you can without the paint vortex coming over the edge of the tin and painting the workshop. If the mixer just fits through the top of the tin, the max speed is around 1500 rpm. If the mixer is small enough to fit a 50mls tin but you are mixing a 250mls tin, raise the mixing speed to around 2000. Make sure the mixer is always fully immersed while revolving. When i painted my frames, I made a metal plate to match the mounting flange of the cylinders and bolted that in place of the cylinders, to mask the area. Any masking would do for this, and you are right. Cylinders should be metal to metal, as should the rest of the frames assembly. Then I masked the sliding surfaces of the horns. Everything else got painted. This is where bead blasting is better than grit blasting. With grit blasting, any dampness in the air can cause flash rusting within seconds. Bead blasting doesn't have anywhere near such an aggressive action and flash rusting is much less likely. You are right in thinking that a number of thinner coats are better than one thick one. Just remember though that using several coats of a colour to get the paint thickness, will give you less than a full gloss finish. That might actually be what you want. Using several thin coats, built up, can give almost any finish from eggshell up to around a 90% gloss. If applying several coats, it is worth experimenting to see what sort of finish you will get as it depends on how thin the paint is, what air pressure you are using, and how far away from the surface the spray nozzle is. Spraying distance can vary the final paint finish from full matt to full gloss too, so it is important when using several coats of thinned paint, to try and keep the spraying distance as near constant as possible. This is not recommended for anyone wanting a matt finish though as the paint will have partially dried between gun and surface, and will lose adhesion. For our work, the ideal spraying distance is around the 2" (50mls) mark, and definitely not more than 3". The amount of thinning and the air pressure should be adjusted to enable spraying at this distance and achieving the wet surface without runs. You can tell if you are too far away as the sprayed surface should appear wet, to flow out, for a short while after the spray cone has moved on, but not wet enough for the paint to make runs. I'm afraid it's practice practice practice, to get the perfect finish. Starting with the frames is good because the finish can be anything from mediocre to excellent and generally they look the same after everything is fully assembled. It's the boiler, tanks and cab that everyone focuses on! Bob. Hi Bob, That's great, I'll make two mixers for the two sizes of tins. I've got both gloss and matt black which I intended to use to have a less glossy finish on the frames. Actually, I don't like the full gloss look on the rest of the locomotive. There was a locomotive like that at the Midlands ME Exhibition, and it really put me off the idea. It looks to Toy like in my opinion, and it must be a nightmare to keep looking good. I'd prefer to take that excessive gloss away. I presume you like the Air Brush for jobs like this because you can work your way around the shapes and angles from a relatively short distance away. It's hard to see how you'd use a larger gun on the inside of the frames and still get into the corners. Would you still use the Air Brush for the Pannier Tanks, even though the sides are quite large areas? The ends and tops have brackets and steps, so I can see why you would want to use the Air Brush for those. It's certainly going to be interesting. Hi Roger. Yes I would use a bottle fed airbrush for all the spraying. It is much more controllable than a fullsize spray gun. Even the half size ones are still unweildy compared to the airbrush. A bottle full of paint, in the aibrush, should be more than enough to paint one side tank, though I wouldn't fill it more than half full as there is a tiny airhole in the lid, and when full, paint can leak out when the airbrush is pointing downwards. The airbrush can also give a much finer finish than a fullsize spray gun. Bob.
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Post by 92220 on Jun 6, 2020 8:24:05 GMT
Hi Roger.
When the mixer is in the tin and it is held in the jig you printed, just gently bring down the drill quill, while revolving, to just rub on the bottom for a few seconds. The mixer will get close enough into the corner to drag out the pigment. Unless the paint has been standing for 2 or 3 years, the pigment won't have gone so hard that a few seconds won't get it loosened. If it is old paint, either break it loose with a screwdriver, as you suggested, or just run the mixer scraping the bottom for around half a minute, at around 1000 rpm. Once loosened, raise the mixing speed to the highest you can without the paint vortex coming over the edge of the tin and painting the workshop. If the mixer just fits through the top of the tin, the max speed is around 1500 rpm. If the mixer is small enough to fit a 50mls tin but you are mixing a 250mls tin, raise the mixing speed to around 2000. Make sure the mixer is always fully immersed while revolving.
When i painted my frames, I made a metal plate to match the mounting flange of the cylinders and bolted that in place of the cylinders, to mask the area. Any masking would do for this, and you are right. Cylinders should be metal to metal, as should the rest of the frames assembly. Then I masked the sliding surfaces of the horns. Everything else got painted. This is where bead blasting is better than grit blasting. With grit blasting, any dampness in the air can cause flash rusting within seconds. Bead blasting doesn't have anywhere near such an aggressive action and flash rusting is much less likely.
You are right in thinking that a number of thinner coats are better than one thick one. Just remember though that using several coats of a colour to get the paint thickness, will give you less than a full gloss finish. That might actually be what you want. Using several thin coats, built up, can give almost any finish from eggshell up to around a 90% gloss. If applying several coats, it is worth experimenting to see what sort of finish you will get as it depends on how thin the paint is, what air pressure you are using, and how far away from the surface the spray nozzle is. Spraying distance can vary the final paint finish from full matt to full gloss too, so it is important when using several coats of thinned paint, to try and keep the spraying distance as near constant as possible. This is not recommended for anyone wanting a matt finish though as the paint will have partially dried between gun and surface, and will lose adhesion.
For our work, the ideal spraying distance is around the 2" (50mls) mark, and definitely not more than 3". The amount of thinning and the air pressure should be adjusted to enable spraying at this distance and achieving the wet surface without runs. You can tell if you are too far away as the sprayed surface should appear wet, to flow out, for a short while after the spray cone has moved on, but not wet enough for the paint to make runs. I'm afraid it's practice practice practice, to get the perfect finish. Starting with the frames is good because the finish can be anything from mediocre to excellent and generally they look the same after everything is fully assembled. It's the boiler, tanks and cab that everyone focuses on!
Bob.
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Post by 92220 on Jun 5, 2020 21:14:26 GMT
Hi Roger.
Don't bother making one of those. They only work because there is no settled sediment in the tin. It's all liquid and the pigments already in suspension. The little wire mixer scrapes the settled pigment up off the bottom of the tin and mixes it in. Shaking just won't do that. As far as leaving the mixer in longer than the suggested 5 minutes. It won't do any harm at all.
As a little bit of an expansion on that, as far as you remembering the half hour mixing time, that is how long it takes to mix a tin of paint and get every bit of pigment fully into suspension....and that is using a spatula shaped hand mixer. Just as a point to add to that, if you use a screwdriver to mix paint, like some try to do, that will NEVER mix in all the pigment, because being a thin, round, 'blade', it just cuts it's way through the paint and doesn't cause it to move around the tin to get the pigments up into suspension, unless it is moving at the sort of speed the little wire mixer in the pillar drill does.
Edit: Sorry, this ended up not in the place I expected. I was referring to not bothering to make the gadget for shaking the paint tin, like they use in the decorators store.
As far as filling in the drilled holes before painting, that is really up to you. I assembled my frames, then grit blasted them, then gave them a coat of Corroless 'S' Rust Stabilising Primer, then applied the top coat. That was 18 years ago and not a trace of corrosion now. 2-pack etch primer would do the same as the rust stablilising primer, because it has a high proportion of phosphoric acid in the activator, that should kill any flash rusting that appears after blasting, though with the current weather, flash rusting is less likely.
Bob.
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Post by 92220 on Jun 5, 2020 10:21:40 GMT
Nice one Roger!!! What a brilliant idea!!! I shall have to make one. You won't need half an hour mixing. With the wire mixer, at around 1000 rpm, or the highest you can run without the paint spilling over, the paint will mix thoroughly in around 5 minutes.
Bob.
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Post by 92220 on Jun 2, 2020 8:28:04 GMT
Hi Steve.
If you are referring to the Hewson white metal casting of the exhaust injector, the casting is actually fairly close to drawing. I bought one because, at the time, I didn't have a BR drawing. Now I do. Having said that, your injector will be your own work(!!) and it looks superb! I am watching this with great interest as, although I have the Hewson casting, I am still aiming to machine up my own in brass or bronze. Well done. It is great to see someone interested enough in the appearance of their loco to make a scale injector body rather than just fit 2 similar commercial injectors.
Bob.
P.S. Like you, I machine everything, and regard using a file a 'last resort'!!
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Post by 92220 on Jun 1, 2020 11:23:09 GMT
Hi Roger.
The Dyson is "surplus to requirements" so if it packs up it wouldn't be a problem as I have the other one that I use regularly. As far as the grit goes, that wouldn't be a problem either. I've used it to clean up overspill from the blaster in the past, with no bad effects. I also use it regularly in the workshop to suck up all sizes of swarfe, except the largest sprirals, which would catch in the hose, or going around the rather convoluted corners inside.
Bob.
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Post by 92220 on Jun 1, 2020 8:26:16 GMT
Hi Roger.
You are right about the clarity of viewing. It can get a bit murky inside but that is usually due to the inner transparent cover stuck to the window, getting dusty. You vacuum might stop that and keep it clear. I shall be interested to see how it turns out for you. I have a spare old Dyson. That could probably be converted to do the same job as your vac unit.
Bob.
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Post by 92220 on May 31, 2020 9:35:54 GMT
Hi John.
The loco is looking really good now. Super job! When I saw the photos of the transfers, I initially thought they were the ones I had done for Phoenix because we used the same blue transfer paper. When I looked again, they weren't mine. I noticed they are not quite right. If you look at the numbers, the sickle moon shapes in the red areas, are done in Black. On the letters GNR, they are done in White. They should be Black on all the transfers. Maybe with a 0000 sable brush, you could fill in the White moons with Black. It may not be obvious to many, but the few who know, would pick fault, which would be a great shame as your painting is superb.
Bob.
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Post by 92220 on May 31, 2020 8:44:38 GMT
Hi Roger. I'm not quite sure of the reasoning behind making this vortex unit. The way I am seeing it is that you think you will lose grit from the unit. The only reason I have ever added grit to my blaster, is when I dump the mucky stuff and fully replace it with new grit/beads....probably once a year. A small amount of dust gets out to atmosphere, but not enough to be of concern. The only problem I experience with my unit is that the window regularly gets dusty and so viewing isn't so good and I have to regularly dust it with an old piece of toweling. I do lose grit out around the bottom cover of the funnel base, but I keep a plastic crate underneath to catch what creeps out. Again, I probably have to empty grit from the crate about once a year. Even then it's only about a litre in that time. I do like the idea of being able to adjust the grit flow, and air flow,to the gun though. That will be quite an advantage with a smaller gun nozzle. Bob. Hi Bob, It sounds like you don't use a vacuum on yours then? If it's dusty and you remove the air, then surely you're bound to lose a significant amount of grit? Hi Roger. No I don't use a vacuum. I just have the filter unit that came with the cabinet. Like yours, it's at the opposite end to the door, so doesn't get cleared very often. I haven't lost any grit, and the fine dust almost all stays inside the cabinet until I open the door to remove the parts that have been blasted. The only way I lose grit is when it works it's way out of the bottom of the base funnel. As you have pointed out, the seal is rubbish! That is why I permanently have a small plastic crate underneath, to catch the grit. When I bought the cabinet I bought a 25Kg bag of beads, some 5 years ago. I still have over half a bag left and have yet to top up. These cabinets are very cheaply made. I may well be lucky to have found a good one. When new, they certainly need all the joints of the sheet-work sealed with silicone bath sealer or you do lose a lot through the joints. Bob.
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Post by 92220 on May 30, 2020 12:11:37 GMT
Hi Roger.
I'm not quite sure of the reasoning behind making this vortex unit. The way I am seeing it is that you think you will lose grit from the unit. The only reason I have ever added grit to my blaster, is when I dump the mucky stuff and fully replace it with new grit/beads....probably once a year. A small amount of dust gets out to atmosphere, but not enough to be of concern. The only problem I experience with my unit is that the window regularly gets dusty and so viewing isn't so good and I have to regularly dust it with an old piece of toweling. I do lose grit out around the bottom cover of the funnel base, but I keep a plastic crate underneath to catch what creeps out. Again, I probably have to empty grit from the crate about once a year. Even then it's only about a litre in that time. I do like the idea of being able to adjust the grit flow, and air flow,to the gun though. That will be quite an advantage with a smaller gun nozzle.
Bob.
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Post by 92220 on May 30, 2020 9:21:54 GMT
Brilliant bit of printing Roger! It's amazing that a machine for DIY use can produce something that big!
Bob.
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Post by 92220 on May 27, 2020 10:07:15 GMT
Hi Martyn.
Thanks for that info. As they say....You live and learn!!
Bob.
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Post by 92220 on May 27, 2020 10:04:02 GMT
Hi Folks.
I switched the computer on yesterday, to get some old loco drawings off it, and got a bit of a surprise. It started to do an Operating System Update. I have Windows 7 on that computer and I was under the impression that Microsoft had stopped sending out updates for Windows 7, back in January. Am I right or wrong?
Bob.
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Post by 92220 on May 27, 2020 8:25:31 GMT
The hose-end attachment on my workshop Dyson, exactly fits the tee-slots, so that has been really handy! Wouldn't be without my Dyson. It's the most used tool in the workshop............sometimes!! Damn! Must find time to clean that floor.
Bob.
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Post by 92220 on May 27, 2020 8:03:16 GMT
Didn't know about the Rocol aerosols. Must try that. Thanks for the pointer.
Bob.
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Post by 92220 on May 26, 2020 8:34:21 GMT
I found lubrication of my Senior Universal mill slideways, problematical. I use a Phoenix Paints Refillable aerosol to lubricate my slideways. Makes it very easy to get oil just where needed. I use butane cigarette lighter gas as the propellant.
Bob.
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Post by 92220 on May 26, 2020 8:23:30 GMT
That's interesting! The horns are on the outsides of the frames, and I thought the 9Fs were the only locos built like that. Were they like that as an un-rebuilt loco? I would think it makes the frame plates a bit close for working on inside motion and cylinder though, in 3.1/2" gauge. Hope you have miniature fingers!!!
........and Thanks for a very interesting thread!
Bob.
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Post by 92220 on May 24, 2020 7:50:31 GMT
Oh dear!!! Never mind Roger. We all make that sort of mistake sometime. So easy to do!! That's really handy that you can print threads, and a great idea for moving the blast cabinet around.
Bob.
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