Monday, 10 March 2014

Cheap balsa wood and PVA do not work well together

Today I tried to build another prototype L-shaped built-up area model. As planned I used PVA glue in place of the superglue I had previously used ... and found that PVA glue does not work well with the cheap balsa wood that I was trying to use. Almost as soon as the glue came into contact with the thin balsa wood I was using for the 'skin' of the model buildings, the wood began to curl and I had to clamp the pieces together with bulldog clips ... which then made some unsightly indents into the balsa wood. (Cheap balsa wood tends to be soft and lighter in colour than the better quality stuff.)

I am therefore left with a dilemma; either to continue to use superglue - and have concerns about the strength of the glued joints - or to persevere with the PVA glue ... and buy better quality balsa wood or find a suitable replacement such as thin bass wood or plywood.

At the moment I am giving serious thought to pursuing the latter course of action as I think that the resulting models will be of better quality.

20 comments:

  1. You could try using wood glue maybe? That's usually a bit thicker than PVA.

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  2. What if you inserted pieces of wood inbetween the balsa and the clamp to distribute the force and apply it evenly to avoid the marks.

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  3. I would use an impact adhesive such as Bostic or Evo-stick.

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  4. Conrad Kinch,

    Thanks for the suggestion.

    I was actually using a PVA-based wood glue and I suspect that the problem is more to do with the quality of the balsa wood than the glue. The water in the glue just seemed to soak into the balsa wood very quickly, causing the curling as it did. I think that a move to a harder wood would solve the problem.

    All the best,

    Bob

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  5. Ross Mac,

    What an excellent suggestion! I will give it a try the next time I use the softer balsa wood.

    All the best,

    Bob

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  6. Jim Duncan,

    Thanks for the suggestion.

    I will try the PVA wood glue and harder wood option first, but if that does not work I will give impact glue a tryout.

    All the best,

    Bob

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  7. I've been using Bostick general purpose adhesive for almost everything apart from applying flock and other than stringing a bit have had no problems with white metal,card,balsa,mdf and kallistra plastic.

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  8. Nigel Drury,

    Another vote for Bostick!

    Perhaps I will give it a try before trying the PVA wood glue and harder wood option.

    All the best,

    Bob

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  9. In my somewhat misty youth when railway modelling and making balsa aircraft were my passions I seem to remember tubes of glue specifically for balsa wood. Now it was evil smelling and I think a good substitute for magic mushrooms. Heady stuff and probably why it no longer seems to be available. If you google balsa cement most folks recommend wood glue for the thicker stuff and super glue for smaller joints.

    To avoid denting when you clamp use corrugated card used for making boxes between the balsa and the clamp jaws.

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  10. oh dear I just googled balsa cement instead of balsa glue. It's still available by various manufacturers. (no wonder so many kids still make balsa models :) ) found a supplier here http://www.shop4glue.com/balsa-cement-glue-28ml-tube-starspan-vintage-formula-traditional-model-plane-kit-adhesive-282-p.asp

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  11. Robert De Angelis,

    I remember that stuff! It really was very pungent ... and I am sure that I got higher than the model aircraft ever did! It was also very, very stringy (even worse then Bostik, of which I think it is a cousin) but it did work.

    I will look out for some good old balsa cement ... but I wonder why it was called cement and not glue?

    Thanks for the tips about how and where to use the two types of glue, and how to avoid denting the balsa wood.

    All the best,

    Bob

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  12. Robert De Angelis,

    Thanks for the link. I may well buy some just for old time's sake!

    It would appear that good old Humbrol still make balsa cement ... but the warning on their website is rather off-putting:
    'Highly Flammable. Vapours may cause drowsiness and dizziness. Irritating to eyes. Keep out of reach of children. Keep away from sources of ignition - No Smoking. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. Do not breath fumes, vapour or spray. Keep container tightly closed and in a well ventilated area. Use under adult supervision. Use in well ventilated area. Use under adult supervision. Use in well ventilated area. If swallowed seek medical advice and show this container.'

    Sounds like they haven't changed the formula one little bit, does it?

    All the best,

    Bob

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  13. As another alternative, try UHU glue, similar to Bostik, but slightly more liquid and I find it gives a much stronger join over time. The other option is to use Artists mounting board rather than balsa. That sticks fine with craft PVA. You may have to laminate it for thicker sections, but that is easy. Cuts very cleanly with a sharp knife - I always use a scalpel. If you remember the original building you saw on my portable war game board, that was the material they were made from

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  14. Ian Dury,

    Thanks very much for the suggestions.

    Do they still make UHU glue? I did not know that! If I see some I will buy it and give it a try. Likewise the mounting board, of which I have a small supply in my modelling stuff ... somewhere!

    All the best,

    Bob

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  15. There was a method used back in the day that may work for you, but it a source of immediate gratification.

    Once you have the parts you want to glue apply the glue to sides to be glued smooth the glue completely onto the surface of the area. Allow the glue time to dry. After the glue has set apply more glue and put your pieces together. This should work for either PVA or "Super" glues.

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  16. Tomo,

    Thanks for the tip. I have never heard of the technique before, but it sort of makes sense and I will definitely give it a trial.

    All the best,

    Bob

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  17. Bob,

    UHU is very much still around. I buy mine in large tubes from the Pound shop.

    Mike

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  18. Mike,

    I actually bought some UHU glue in Poundland myself this afternoon!

    It was news to me that it was still being made ... and I have some joints that I have glued with it curing as I write this comment. (I saw no reason to waste time before trying it out ... and so far it seems to be working quite well.)

    All the best,

    Bob

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  19. How about glue with superglue as before but when it has dried paint the whole model with PVA?

    It would act as extra glue/ support as well as a sealant so the paint wouldn't soak into the wood either?

    Just thinking out loud really....

    Cheers,

    Pete.

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  20. Pete,

    As I would seal the completed model with PVA glue before painting it, you suggestion makes a lot of sense.

    My recent experiments with different glues has not been as successful as I had hoped, and going back to using cheap superglue makes a lot of sense.

    All the best,

    Bob

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