Translation:Shulchan Aruch/Orach Chaim/255

1. The Laws Governing the Preparation of Fire before the Onset of Shabbos, 3 Seifim: It is forbidden to make a large fire – a medurah – using wood as fuel close to nightfall [on Friday] unless the fire catches hold to the extent that the flame burns on its own accord without the assistance of other wood (I.e., flaming wood from an outside source.) If [only] one log is [burning], the fire must take hold of the majority of its circumference and its width. If it is not kindled as such (like above) it is forbidden to make use of it on Shabbat. This is a decree, lest one stir [the wood] on Shabbos, moving [the pieces of] wood until the flame ascends on its own accord. If, however, [the wood] was kindled to the extent described [in the previous subsection] while it was still day, a person may warm himself by [that fire] and use its light, regardless of whether [the wood] was [burning] on the ground or on a holder for fire. And even substances that are forbidden to be used as wicks for [the Shabbos] lights.

2. There are authorities who maintain that if coals [are used for kindling], even though the fire only started burning minimally [on its own while it was still day on Friday], it is permitted [to benefit from it], because they will continue to burn on their own.

3. When tar, sulfur, straw, or stubble [are used as kindling for] a medurah, even though the fire only started burning minimally [while it was still day on Friday], it is permitted [to benefit from it, because these substances will continue to burn on their own]. The same [rule applies when] reeds or date pits are used as kindling when they are spread out. If, however, the reeds are bound [in a bundle] and the pits are [collected] in a basket, then the fire must take hold of them to the extent that it ascends on its own accord, and there are those who say the opposite.