RMweb Premium 47137 Posted May 6, 2012 RMweb Premium Share Posted May 6, 2012 I have taken to painting brass handrail wire and knobs (assembled into position) with a trace of "super glue" as a preparation for painting with ordinary enamel. This seems to work, as a cheap DIY substitute for an etching primer, which I couldn't justify buying for such a tiny paint job. Could someone with some knowledge of chemistry or whatever tell me whether I am potentially onto a good thing here, or more likely building up trouble for myself? The glue is the very thin variety sold 8 tubes for a pound in bargain shops, and left to cure for a few hours before painting. The top coat is Railmatch enamel ("contains lead chromate"). The 'brush' for the glue is a cotton bud. - Richard. Link to post Share on other sites More sharing options...
bertiedog Posted May 6, 2012 Share Posted May 6, 2012 Superglue chemically is virtually liquid perspex, and only naturally grips anything by exclusion of air, and a close fit, on brass it coats the surface. On the other hand an etching primer for brass would somewhat "clean" the surface by the mild acid etching action, and improve the adhesion of the paint. Paint adheres well to superglue, and perspex, and the use described would work, but make sure the brass is properly clean with a good strong solvent like acetone first, any trace of oil and the grip is compromised. Stephen.. Link to post Share on other sites More sharing options...
Rumblestripe Posted May 6, 2012 Share Posted May 6, 2012 As I understand it, a "set" or "cured" cyanoacrylate glue leaves a thin layer of an acrylic resin. As such it would not react to the enamel paint or its binder or solvent. So it is "safe". That said I'm not sure that you are gaining much as although the superglue will firmly bond to the brass, I'm not convinced that the paint will bond to the glue to any significant degree? Link to post Share on other sites More sharing options...
Kenton Posted May 6, 2012 Share Posted May 6, 2012 any trace of oil and the grip is compromised. and for clarity here "oil" is a general term for grease, oil and any organic substrate including finger prints. Link to post Share on other sites More sharing options...
bertiedog Posted May 6, 2012 Share Posted May 6, 2012 Enamel and cellulose paints and water based paints will grip cured Superglue, which as said, is a type of perspex, which is an acrylic plastic. So if the paint will grip perspex it will grip set superglue, water based paints have the most dificulties, but acrylic paint should be all right. What they might not grip is Loctite, which in normal types is an air exclusion setting product, and may remain liquid at the edge of a joint. The excess can be removed with sovent, or accelerators. By Loctite, I do not mean "superglue by Loctite Brand", but the specialist thread retainers and glues made by Loctite.(eg 601 et all). An odd use for superglue is sealing wood, it is an expensive way to do it, but thourough and very tough. It is used by wooden pen makers to seal the wood pen body to a high polish acrylic surface. It can also spot repair a wood surface, or seal wood filler on a damaged wood finish before painting over to disguise the repair. In this use it certainly grips the paint very well. Stephen. Link to post Share on other sites More sharing options...
RMweb Premium 47137 Posted May 6, 2012 Author RMweb Premium Share Posted May 6, 2012 This is all encouraging - thank you What they might not grip is Loctite, which in normal types is an air exclusion setting product, I am happy to concentrate on the cyanoacrylate adhesives which set in the presence of moisture (for example, in air) ... I suggest thread lockers like 601 would not be appropriate for this but it is still useful to mention them in case someone picks this up months from now. In my case, I primed the plastic model (with an acrylic aerosol car primer), then fitted the brass parts, primed them (super glue) and then put top coat on the whole lot. Given the information above, I think next time I will assemble everything, apply the 'glue primer' to the brass parts, and then prime the whole model with the aerosol. - Richard Link to post Share on other sites More sharing options...
trisonic Posted May 6, 2012 Share Posted May 6, 2012 Almost completely off - topic. Eric Clapton is one of the few pro players who does not like nitro - cellulose finish on his guitar necks - all his current stage guitars (non-vintage) necks have been finished with cyanoacrylate adhesive, which is quite unusual in the guitar-playing world. Best, Pete. Link to post Share on other sites More sharing options...
RMweb Premium 47137 Posted May 7, 2012 Author RMweb Premium Share Posted May 7, 2012 The 'brush' for the glue is a cotton bud. I should point out - the combination of cyanoacrylate with cotton is widely reported as creating an exothermic reaction. It would be sensible to use a different method of application (perhaps a wooden cocktail stick?), though this ought to be fairly academic with the quantities involved for a brass handrail. Link to post Share on other sites More sharing options...
N15class Posted May 17, 2012 Share Posted May 17, 2012 Enamel and cellulose paints and water based paints will grip cured Superglue, which as said, is a type of perspex, which is an acrylic plastic. So if the paint will grip perspex it will grip set superglue, water based paints have the most dificulties, but acrylic paint should be all right. Stephen. I do not know about acrylic paint sticking to Perspex. But acrylic base glues do not like sticking to it. Link to post Share on other sites More sharing options...
bertiedog Posted May 17, 2012 Share Posted May 17, 2012 I do not know about acrylic paint sticking to Perspex. But acrylic base glues do not like sticking to it. They do not "bind", with the perspex, they adhere, as with all paints by air exclusion, and with polished surface perspex the grip is pretty poor with most paints. Paints grip by holding on to a rough finish, or air exclusion, or they chemically bond, and acrylic paint only adheres by the first two. Perspex is resistant to most common glues and thinners, Chloroform is the main solvent and glue for Perspex, and is to say the least, dangerous! Link to post Share on other sites More sharing options...
N15class Posted May 17, 2012 Share Posted May 17, 2012 They do not "bind", with the perspex, they adhere, as with all paints by air exclusion, and with polished surface perspex the grip is pretty poor with most paints. Paints grip by holding on to a rough finish, or air exclusion, or they chemically bond, and acrylic paint only adheres by the first two. Perspex is resistant to most common glues and thinners, Chloroform is the main solvent and glue for Perspex, and is to say the least, dangerous! Think you miss understood, I was not sure how well acrylic paints would adhere to Perspex, as acrylic based glues do not stick. I was not talking about glueing acrylics together. Link to post Share on other sites More sharing options...
RMweb Premium 47137 Posted May 18, 2012 Author RMweb Premium Share Posted May 18, 2012 Paints grip by holding on to a rough finish, or air exclusion, or they chemically bond, and acrylic paint only adheres by the first two. I was not sure how well acrylic paints would adhere to Perspex, as acrylic based glues do not stick. I was not talking about glueing acrylics together. Although cured cyanoacrylate is chemically similar to perspex, perhaps its surface texture is rougher than that of perspex, and this roughness helps the glue to provide a suitable substrate for the paint. Whatever the reason, I am using a solvented paint (Railmatch) and this does seem to hold. I suspect the class of paints which are called 'acrylic' is so wide it would be a bit ambitious to try to categorically say whether they will or will not bond to a particular substrate. Link to post Share on other sites More sharing options...
N15class Posted May 18, 2012 Share Posted May 18, 2012 That is the main thing, as long as the glue sticks to the brass and the paint sticks to the glue. The rest does not matter. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.