Talk:Varnish

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Varnish is also a class of hydrocarbons, I believe. In particular, if you leave a gasoline engine unused for a long time, it is said that the gasoline will settle out into gums, resins, and varnish. This meaning of the word is not explored in this article, but I don't have the knowledge to fill it in at this time --Mdwyer 22:20, 2005 September 6 (UTC)

I don't know about the gasoline. It seems entirely possible due to oxidation. Inside the cylinder or on other moving parts people talk about a "glaze" and "breaking the glaze" by a light abrasion or sanding when you're trying to avoid actual machining in an engine overhaul. The glaze is basically the burned hydrocarbons deposited on the metal where the friction or heat occurs.

[edit] Difference between Varnish and Shellac

shellac is NOT a varnish. varnishes, as the article points out, undergo chemical reactions after application. shellac does not. it is a so-called 'solvent release' finish. i.e., the solvent evaporates and leaves a film of the unchanged resin, which always remains soluble in the original solvent. in the case of shellac, this is methanol.methanol will remove a shellac finish.similarly, if a shellac finish is remove by scraping, the resulting powder can be dissolved in methanol and re-used. (i don't recommend it, but it is possible.)worn, crazed and otherwise damaged shellac finishes are also amenable to a treatment called re-amalgamation, where a coat of the solvent is applied (usually by sparaying) and simply allowed to dry. this cannot be done with varnishes. methanol and other alcohols have little or no effect on a varnished surface. i will wait to hear additional comments, but after a time I am going to delete shellac from this article, unless convinced otherwise.Toyokuni3 (talk) 17:07, 4 May 2008 (UTC)

I'm a contributor to this article but I haven't kept up with my WP ID. What you point out is absolutely true, and it is a weak point in the article. However, the original item that got the name of varnish oh-so-many centuries ago was re-soluble in its original solvent, just as shellac is. Dammar is one example of this and is widely available in art supply stores today.

One problem with understanding varnish is in semantics. Another is in chemistry. Frankly, varnish has not garnered much interest among the academicians who might clarify all the terminology. Conversely, varnish has been for centuries primarily an item of industry: people who are trying to make some (often not much) money but who are not concerned with regularizing terminology. Suffice it to say that today, in modern terms, "varnish" means any, and absolutely any, clear or semi-clear medium for providing a hard or semi-hard finish. —Preceding unsigned comment added by 76.198.65.250 (talk) 07:34, 4 June 2008 (UTC)

That is an excellent point and one I've suspected since I started looking into these technologies. Working out the semantics between pages like varnish, shellac, enamel, and lacquer has been rough as authoritative sources such as dictionaries are nonspecific, and professional sources tend to conflict depending on geographic region and publication date. In these cases the best we can do is set up arbitrary or at least "best effort" scopes for article content. Concepts like "for the purpose of this article <topicname> refers to <chosen definition>". I've forgotten the state of this particular article, but from what I see, I agree, in modern terms, varnish refers to any clear or semi-clear medium for providing a hard or semi-hard finish. Shellac can fall into this category, but there is no need to describe shellac in detail, simply a quick WP:SUMMARY and reference to the main shellac article, and possibly explaination of how shellac does not fall into certain definitions of varnish. -Verdatum (talk) 15:59, 4 June 2008 (UTC)