+> I like making this configurable. I do fear that changing what's included
+> by default could break some existing uses of teximg? That needs to be
+> considered, and either the breakage documented in NEWS, or avoided. Also,
+> if mchem is dropped, I think the suggests on texlive-science in
+> debian/control should probably go? --[[Joey]]
+
+>> Yes, changing the defaults could break some existing uses. I think in
+>> this case, documenting in NEWS and dropping texlive-science is the
+>> best option. In fact, NEWS should probably document the config
+>> setting to return things to how they were.
+>>
+>> The reason I prefer dropping `mchem` rather than keeping it is that `mchem`
+>> is non-standard. Now that things are configurable and it is easy to
+>> add in if you want it, having only standard packages by default is a
+>> good thing. Here is a proposed NEWS entry:
+
+File: TexImg standard preamble changed
+
+The [[plugins/teximg]] [[plugin]] now has a configurable LaTeX preamble.
+As part of this change the `mchem` LaTeX package has been removed from
+the default LaTeX preamble as it wasn't included in many TeX installations.
+
+The previous behaviour can be restored by adding the following to your ikiwiki setup:
+
+ teximg_prefix => '\documentclass{scrartcl}
+ \usepackage[version=3]{mhchem}
+ \usepackage{amsmath}
+ \usepackage{amsfonts}
+ \usepackage{amssymb}
+ \pagestyle{empty}
+ \begin{document}',
+
+In addition, the rendering mechanism has been changed to use `dvipng` by default.
+If you would like to return to the old rendering mechanism using `dvips` and `convert`
+then you should add the following line to your ikiwiki setup:
+
+ teximg_dvipng => 0,
+
+The LaTeX postfix is unchanged, but is also now configurable using `teximg_postfix`.
+Happy TeXing.
+
+>> I think that about covers it. -- [[Will]]
+