Jimlad

Thanks for the responses, appreciated. The equipment choice was inspired by Paul Budzik's youtube channel 'Scale Model Workshop' and this video here discusses the rationale behind this particular gun set-up. I also have a smaller traditional airbrush for smaller models and I typically only use both guns for base coats. The paint stirrer now seems like a good idea and I'll look into getting hold of one, although I also have a lab mixer so might be time to wheel that out. I use a pipette to add paint and thinners to either the gun cup or a shot glass, in a fairly makeshift manner and then I'd give it a wiggle with a coffee stirrer or tongue depressor until it looked about right (milky). This will be the first habit I'll need to change - I had an image in my head that the thinners would evaporate off and things would even out, it's clearly not as simple as that. I'd typically run out of paint and then mix up another batch - probably at different ratio's. I did wonder about the pigment/paint thing and it seems that there's also a slight variation in shades across different tins. In terms of the white base coat I've experimented with loads of car body primers and model making primers (often more suited to typical model making polystyrene plastics than PU) and I couldn't find one that was any better than just straight Humbrol enamel. Humbrol do a grey paint called 'primer' however it's just grey paint and has no particular attributes other than colour which would differentiate it. With that in mind I thought why not just use the top coat as the primer or base coat and apply it lightly at first. If I used white for instance as a base coat because I wanted it to show through slightly to give a brighter orange top coat I'd need to get the opacity very even across the whole top surface which is quite tricky on a larger model. Perhaps though another reason to use a different colour base coat is to be able to easily see where the top coat is evenly sprayed, not sure but opinions welcome, however in this case I needed to match the colour of a previous work. Thanks again.

Hello all, Can anyone suggest what I might be missing here, I'm spraying a polyurethane model which I've cast myself using Humbrol matt enamel 82 (lining orange) via an Iwata RG3L gun with a 1mm tip. Air pressure is approx 30 psi at the gun and the recommended working PSI is around 35. The model has lots of large flat areas and is approximately A4 size and 75mm deep. No primer and no release agents were used in the mould. I'm aware that spraying to far away results in paint drying too quick and this can leave a furry suede like result, so I'm spraying from approximately 3 inches away, I'm not getting any runs. However I still have a furry surface which isn't entirely even, with some areas looking more furry than others. My suspicion is that I'm not consistently or properly diluting the paint with Humbrol thinners, sometimes I've diluted it in the spray gun cup by eye, (approx 1 to 1) and sometimes separately and not always to the same ratio's. The model has been repaired and the base plastic colour requires a lot of paint to cover up these repairs, so I'm wondering also whether there's just too much paint on it. I'm trying to put just enough on (in between drying intervals) to just cover these discrepancies. Finally, do you have any thoughts on what to do next, I was thinking of very lightly attempting to de-nib / de-fur it with high grit abrasive? Sorry for the long tedious post.

Thanks very much for the replies on this. I'll probably try some of the colourcoats stuff. Taking a quick look at the costs of the recommended products per litre. Humbrol comes in at £45 Xtracolour at £36 Coloucoats at £30 Then there's the courier cost as typically they can't be sent by royal mail... I subscribe to a youtube channel called Scale Model Workshop, he has an interesting vid on primers and the sort of thinners he refers to there are of the more industrial variety. I wondered if there were equivalent uk alternatives. Thanks again. J

Turps huh? Interesting. Would that be the common or garden diy shop stuff? I always thought that might leave a residue. Or would I be better off with distilled? Thanks Dave.

I get through a lot of their thinners so I buy them in the 125ml size, more expensive than champagne - anyone have any tips on where to buy? Rustins tech support suggested just using white spirit however I wasn't convinced. I'm open to suggestions for different products... Thanks.

Hello, Has anyone got any thoughts / knowledge they might share on paint primers that bond well to PU resin. I've tried over a dozen and I'm familiar with prep, degreasing sanding etc. I will more than likely be using enamel paint over the top. Thanks.

This post is a bit old now but I'll chip in case anyone is interested. In answer to the original questions regarding degassing in the mold or the pot, it's fine to degass in the pot and you can do it in several stages when working with silicone rubbers if your chamber isn't big enough. So you don't have to mix it all in one go. Typically most rubbers will be left overnight and there should be enough pot life so you don't have to panic when mixing and degassing, however if you haven't done it before I'd recommend selecting one with a fairly generous pot life as the thorough mixing can take a while. Speaking to one of the Notcutt reps might be useful in terms of recommendations but perhaps Silastic RTV 3481. You might be aware there are two main types of silicone rubber, tin cured (condensation) and platinum cured (addition), as the names suggest the platinum one is more expensive however you'll get many more 'pulls' from it although it's a bit more pernickety to work with. As regards degassing the resin, you might find you don't need to, if your cast has lots of undercuts or areas where bubbles might get trapped you could try a sort of slush casting approach, where you mix up a small amount of resin and swill it around in the mould in order to coat the surfaces first - wait for that to cure and pour the remainder of the resin. Most PU resin's tend to be a creamy or amber colour when mixed unpigmented, there are a few that cure white and a few that cure clear. If you're going to be painting these things you'll need to think about what resin takes paint better (maybe SG2000) and obviously you wouldn't need a clear version. That's probably too much info but perhaps useful to someone.

I'm trying to imagine it for practical use for direct mixing of small quantities of paint. Would you still manually mix an estimated shade which once dry the Nix device would give you say a cmyk (?) breakdown of your target colour in comparison to your mixed colour. Let's say the mixed colour has too much yellow and black you'd then what, add more of the cyan and magenta to adjust the ratios... hmmm, cmyk models are used in print but are they useful for mixing artists acrylics or enamels? You'd probably need white as well. Whatever colour space was used wouldn't you need standardised base colours to mix from? So I'd be interested Jamie in how you use it in your workflow, lets say you check a colour of paint and it's not quite right do you eyeball and adjust it based on experience or start again...? Or do you have a really expensive paint mixing machine that does it all for you ...🙄

Thanks all for some really interesting replies. Thoughts in response; Daylight, even at midday in ideal weather conditions, bounces all over the place indoors and isn't ideal which is why photographers use studio flash etc for colour critical stuff. I'm not trying to match to industry standards ral/pantone etc. I'm trying to match the colour of an object to that of paint and I'll evaluate it once dry. My colour perception is ok but even if it were off I'm matching to my own perception not a colour model. (Thanks for the links). I have an x-rite Colormunki spectrophotometer thingy (more aimed at print profiling) and I'm familiar with digital colour profiles etc, but my eyes are more convenient and I think I'm after a simple viewing area (box?) which minimises other light and gives a consistent daylight / full spectrum illumination. Having said that, that nix sensor looks really handy, have you got the more expensive version Jamie? I'd be interested in how you use it in a workflow. I wonder if a couple of full (96% or higher) spectrum bulbs would suffice (thanks for those links Brian) but damn that Nix thing has got me interested. My workflow at present involves cutting up some white scrap card into small strips, mixing colour and painting it onto the end of a strip then holding this up right next to the object I'm trying to match to. Too warm or too whatever and I make adjustments and hold it up again until I'm satisfied. This is then sprayed onto a primed cast which dries quickly and is then evaluated again against the object/original. Frequently this is all done multiple times until I get a very close match. The spray booth and mixing area are at different areas in the room and it can be a bit laborious... Cheers, Jim

I'm trying to evaluate paint colour and get it to closely match source materials. One of these would be handy, however my budget is more towards this. I appreciate this won't be a concern for many but wondered if anyone has found an affordable way to light/view their work in a consistent reliable way?

I use one of these sort of things because space is a problem for me; https://www.amazon.co.uk/dp/B003UMZQ4U/ref=cm_sw_em_r_mt_dp_U_TdXOEbHP992P5 and it lets light in. It collapses flat quickly and is lightweight. I had already an industrial type workshop air filter/fan which extracts via a hole I've made at the back. Filters from ebay which I cut into circles using the front grill as a template. If I had the space for somewhere to permanently install it I'd probably try something like this which ideally would extract to the outside..