J'ouvre un sujet ici concernant un probléme que pas mal de personnes ici risquent de rencontrer tôt ou tard , vu que l'utilisation de bouche pores epoxy et de vernis a l'eau et ou de finitions huilées se démocratise
En Anglais on appelle ça : "epoxy amine blush" , c'est le terme à rechercher dans google
Pour ma part j'appellerais ça : des putins de bubulles
Tout d'abord un texte explicatif (en Anglais , si une bonne âme se sent de traduire le pavé...) trouvé sur le site des luthiers Australiens et Néo Zélandais:
Lots has been written on the variouse fori about both Zpoxy and West Systems products being used for grain filling guitars and both will work very well if you are very careful with their use.
My own experience with epoxy sensitization led me to discover that West System products are formulated very much towards industry. This is a company which needs to be very careful with the use of amines in their hardeners and limit know sensitizers where ever they can if they wish to stay in business. The end-user in their target market (boat builders) are very likely to be exposed to epoxy products on a daily basis and it is accepted that sensitization drives the affected out of the industry permanently. It is interesting that West Systems does make an 'amine free' epoxy, a more expensive process I am led to believe, but the fact that they can and do gives some insight into their operation and ethics.
Zpoxy on the other hand is targeted at the hobbyist, no need to bother too much here about daily exposure so the product is very much amine based because it's simply cheaper to make it that way. Aside from the greater risk to sensitization these cheaper products pose, amine blush can also be a problem so you need to consider this at the checkout.
Amine blush is a byproduct of a chemical exchange between amino acids (amines), carbon dioxide, and moisture in air. When epoxy is mixed, applied and cured in the presents of these elements, the amines in the hardener which are responsible for 'acid' curing the resin also react to cause an unwanted byproduct.
This byproduct being less dense that the resin will then work it's way through the mix excreting like a dew upon the surface until the mix has completely cured. It presents in a degree relative to the amount of carbon dioxide and moisture that had been present in the air and also the speed of the curing process. It's visual appearance can range from an milky blue waxy substance when heavy, to a thin, near invisible oil, that can barely be seen with the naked eye on the surface of the work piece.
Unless fully removed, amine blush will retard or even reverse the curing process of many finishes, particularly those which rely upon polymerization to harden such as traditional oil based varnishes, and rubbing oils like Truoil etc. Even finishes such as shellac and lacquer can be affected by poor surface adhesion. If undetected and an oil finish then applied over the top, the finish can still cure and even be buffed out as intended only to then heart breakingly blister and soften as the weeks go by. The only solution then is a complete refinish....DAMHIKT.
If detected before a finish is applied, amine blush CANNOT be removed from the surface of the work piece by simply sanding with an abrasives, this will only serve to work the blush 'into' the surface and spread it over a greater area. Amine blush can only be removed by washing the surface of the work piece with mild soap and water or cloudy ammonia and water and a nylon scouring pad. Once dry you can then sand or scrape as required and proceed with the rest of your finishing regime as normal.
The best advice to reducing the occurrences of amine blush is to reduce the presents of the three elements responsible for it in the first place. Always apply epoxy in an environment that has lots of 'fresh air' circulation. Avoid breathing directly upon your work during application and mixing, use a respirator (of course) and a fan to push clean air between you and the work. This will serve to keep epoxy fumes away from you, and your carbon dioxide and moisture rich breath away from the epoxy. Apply epoxy only when the ambient temperature is favorable to a fast cure time. Stay well away from the work piece and allow the epoxy to 'fully' cure before reworking and......avoid cheaply made epoxy products that have a heavy amine base to the hardener.
Cheers
Pour faire simple , et reprenez moi si je me trompe , l' "amine" (traduction?) contenue dans le durcisseur des résines epoxy peut se dégrader sous l'action combinée de la sueur , de la friction et de la chaleur et produire un acide , si il y a du dioxyde de carbone et de l'humidité "emprisonné" dans la résine lors du séchage . Il en résulte une réaction chimique avec les produits appliqués dessus , si ceux ci sont du type "polymérisés" (comme nos chers vernis a l'eau et les différentes finitions a l'huile) .
Le résultat : des micros bulles au niveau des pores , la ou se trouve l'epoxy en quantité et cette fameuse "amine" , dans un premier temps , puis les mini bulles deviennent plus grosses , et finalement le vernis se décolle comme du vieux papier peint , ou comme la peau des touristes après un violent coup de soleil . :mrgreen:
Il semblerait que le seul moyen de s'assurer de ne plus avoir d'amine dans sa résine epoxy serait de nettoyer la surface a l'eau savoneuse avant de vernir : tout simplement ! ou d'utiliser un autre type de bouche pores
Si ça peu éviter les malheurs du re-vernissage , c'est pas chers payé :D
Bon et maintenant places au photo , éloignez les enfants et les femmes enceintes de l'écran !
Voilà , tout aide , ainsi que les commentaires d'ordre technique sont les bienvenues
A plus
-m-
je lirai ca a tete reposee ce soir 
ouch 
