Fixing on shields and spears

[archangel1]

I noticed a couple of references to roughing up the surface before glueing.  From my understanding, that is not recommended with cyano glues.  It works fine with epoxy but superglues apparently require the smoothest connection between pieces.  Unfortunately, I can't recall where I found this information.  I'll keep looking.
Also, make sure you aren't using too much glue.  It doesn't work like most regular glues where the more you add, the stronger the join.  Sometimes.

[Antenociti]

I noticed a couple of references to roughing up the surface before glueing.  From my understanding, that is not recommended with cyano glues.  It works fine with epoxy but superglues apparently require the smoothest connection between pieces.  Unfortunately, I can't recall where I found this information.  I'll keep looking.

I think I know where/why/what you have read that advice and its correct ..... in certian circumstances  :

The "theory" behind rough surfaces is that it increases the available surface area for the bond and, in practise, it certainly works for metal and resin and with CA glues - the only time I wouldnt roughen a surface is with wicking application and cements such as poly - such as when used with polystyrene sheets: in those circumstances roughening surfaces doesnt bring benefits as the bond is formed by the glue effectively "melting" the plastic so that the two sheets fuse together. Obviously as such having the sheets smoothly together, and thus allowing the glue to "wick" between them (capillary action) is the best way to bond them - and roughening surfaces will hinder that, although it wont hinder the strength of the join (see later).

What I suspect that you have read though is to do with application of superglue on porous surfaces:

With porous surfaces superglue (non-gels) pentrates the material leaving little of the glue at the surface - that is exacerbated with roughening as it encourages the glue to seep into the material (capillary action again). If you then try to bond two such surfaces the bond will be weaker roughened, than left smooth, as more of the glue will ahve penetrated away fromt he surface being bonded.

Indeed super glue is not at all effective at bonding porous materials unless you use substances to pre-treat the porous material, use gel-type CAs and/or accelerators that dont give the glue time to soak into the porous material, or coatings that specifically prevent the CA soaking into the material.

For any non-porous material though (metal, resin, plastic) then roughening will help.
For porous materials then roughening will hinder and even prevent, adhesion.

Make sense?